Answer:
x= 3 +√509/10
Or
x= 3 - √509/10
Step-by-step explanation:
Given:
5x2-3x = 25
Using completing the square method of solving quadratic equation
Step 1: Factor out the coefficient of the x^2 term.
5(x^2 - 3x/5) = 25
Step 2: Add a number that would complete the square inside the parenthesis and also add this to the other side of the equation.
Take (1/2) of (3/5)
1/2 × 3/5
= 3/10
Square 3/10
We have, 9/100
We have,
5(x^2 - 3x/5 + 9/100) = 25 + 9/100
Step 3: Simplify
x^2 - (3/5)x + 9/100 = 25 + 9/100
5(x^2 - 3x/5 + 9/100) = 5 + 9/20
Step 4:
factor the right side
(x - 3/10)^2 = 509/100
Take both roots
√ (x - 3/10)^2 = √509/100
x - 3/10 = ±√ [509/100]
x = [ 3 ±√509 ] / 10
x= 3+√509/10
Or
x= 3 - √509/10
Nine and one half less than four and one half times a number is greater than 62,5. Which of the following represents
the solution set of this problem?
O (16,400)
O (-16,400)
o (-0,16)
o (-00,-16)
Answer: (16,O0) That is 16 to positive infinity
Step-by-step explanation:
4.5x - 9.5 > 62.5
4.5x > 62,5 + 9.5
4.5x > 72
x > 72/ 4.5
x> 16
So all real numbers greater than 16 is the solution set.
(16,O0)
I wish I had the infinity symbol on this keyboard!
please help with this math question
Answer:
E H
F F
G E
I hope I helped.
Which of the following statements is true for a function with equation Ax) = 5(3)*?
The graph has y-intercept (0,5) and increases with a constant ratio of 3.
The graph has y-intercept (0, 3) and decreases with a constant ratio of 3.
The graph has y-intercept (0, 3) and increases with a constant ratio of 5.
The graph has y-intercept (0,5) and decreases with a constant ratio of 3.
Answer:
Hey there!
The graph has a y-intercept of (0,5), and increases with a common ratio of 5. (For example, it increases from 3, 15, 75, and the common ratio is 5.
Hope this helps :)
Two cities, A and B, are mapped on the coordinate plane. How far apart are they from each other? A. 145−−−√ units B. 97−−√ units C. 5 units D. 73−−√ units
Answer:
B
Step-by-step explanation:
From the graph we can notice that the coordinates of the cities are:
● A(2,3)
● B(6,-6)
There are many methods to figure out the distance between A and B. We will use the distance formula.
Let d be the distance between A and B.
● d = √[(2-6)^2 + (3-(-6))^2]
● d = √[(-4)^2 + (3+6)^2]
● d = √[ 4^2 + 9^2 ]
● d = √(16+81)
● d = √(97)
Answer:
The answer is B) 97 units
Step-by-step explanation:
From the graph we can notice that the coordinates of the cities are:
● A(2,3)
● B(6,-6)
There are many methods to figure out the distance between A and B. We will use the distance formula.
Let d be the distance between A and B.
● d = √[(2-6)^2 + (3-(-6))^2]
● d = √[(-4)^2 + (3+6)^2]
● d = √[ 4^2 + 9^2 ]
● d = √(16+81)
● d = √(97)
Some lemon, lime, and cherry lollipops are placed in a bowl. Some have a
chocolate center, and some do not. Suppose one of the lollipops is chosen
randomly from all the lollipops in the bowl. According to the table below, if it
is known to be lemon, what is the probability that it HAS a chocolate center?
Answer:
45%
Step-by-step explanation:
There are 20 lollilops with lemon in total. 9 of them have a chocolate center. 9/20=0.45. To convert it into percentage you would multiply the number by 100. 0.45*100=45
The answer is 45%
"if it is known to be lemon" means we ignore any other flavor. I recommend covering up the other values, or you could highlight just the lemon column.
We have 9+11 = 20 lemon total. Of this 20 total, only 9 lemons have a chocolate center. So 9/20 = 0.45 = 45% of the lemon candies have a chocolate center.
Find the m∠RLU. A. 20 B. 42 C. 84 D. 10
Answer:
b is the correct answer. p is 10
The value of m∠RLU = 10.
How to estimate the value of m∠RLU?Given: (5p - 8) and (2p + 22)
Simplifying both of the equation, then we get
5p - 8 = 2p + 22
Add 8 to both sides of the equation, then we get
5p - 8 + 8 = 2p + 22 + 8
simplify
5p = 2p + 30
substract 2p from both sides of the equation
5p - 2p = 2p + 30 - 2p
3p = 30
p = 30/3
p = 10.
m∠RLU = 10
Therefore, the correct answer is option D. 10.
To learn more about angles and triangle
https://brainly.com/question/19703680
#SPJ2
The width of a rectangle is 14 feet less than 3 times the length. If the area is 24 fta,
find the width and length.
Width = 4 and Length = 6
Width = 2 and Length = 4
Width = 10 and Length = 12
Width = 6 and Length = 8
Answer:
Width: 4
Length: 6
Step-by-step explanation:
We can create a systems of equations for this problem, assuming W is width and L is length.
W = 3L-14
WL = 24
We can substitute W into the equation.
(3L-14)L = 24
3L²-14L = 24
3L² - 14L - 24 = 0
(3L+4)(L-6)=0
L = 6
Now we can find W by substituting L into the equation.
[tex]6\cdotw=24\\w = 4[/tex]
Hope this helped!
Find the measure of FG. A. 9 B. 10 C. 11 D. 8
Answer:
x =11
Step-by-step explanation:
(whole secant) x (external part) = (whole secant) x (external part)
( 15+x-2) * (x-2) = (19+x-3) * (x-3)
Combine like terms
(13+x) *(x-2) = (16+x) *(x-3)
Distribute
11x+x^2-26=13x+x^2-48
Subtract x^2 from each side
11x -26 = 13x -48
Subtract 11x from each side
-26 = 2x-48
Add 48 to each side
22 = 2x
Divide by 2
11 =x
What effect will replacing x with (x−3) have on the graph of the equation y=x2 y = x 2 ? A. slides the graph 3 units down B. slides the graph 3 units right C. shrinks the graph by a factor of 3 D. slides the graph 3 units left
Answer:
B. slides the graph 3 units right
Step-by-step explanation:
Replacing x with x-h moves the graph 'h' units to the right. In this case, the graph is moved 3 units right by replacing x with x-3.
Suppose a function f has an inverse. If f(2)=6 and f(3)=7, find: f−1(6)
Answer:
[tex]f^{-1}(6) = 2[/tex]
Step-by-step explanation:
Given
[tex]f(2) = 6[/tex]
[tex]f(3) = 7[/tex]
Required
[tex]f^{-1}(6)[/tex]
First, we need to determine the slope of the function using;
[tex]m = \frac{y_1 - y_2}{x_1 - x_2}[/tex]
From the given parameters;
In [tex]f(2) = 6[/tex]
x = 2; y =6 --- Take this as x1 and y1
In [tex]f(3) = 7[/tex]
x = 3; y = 7 --- Take this as x2 and y2
[tex]m = \frac{y_1 - y_2}{x_1 - x_2}[/tex] becomes
[tex]m = \frac{6 - 7}{2 - 3}[/tex]
[tex]m = \frac{- 1}{ - 1}[/tex]
[tex]m = 1[/tex]
Next, we determine the equation of the function using
[tex]y - y_1 = m(x - x_1)[/tex]
Substitute the values of x1,y1 and m
[tex]y - 6 = 1(x - 2)[/tex]
Open bracket
[tex]y - 6 = x - 2[/tex]
Add 6 to both sides
[tex]y - 6 + 6 = x -2 +6[/tex]
[tex]y = x + 4[/tex]
Next is to determine the inverse function by swapping the positions of x and y
[tex]x = y + 4[/tex]
Make y the subject of formula;
[tex]y = x - 4[/tex]
Replace y with [tex]f^{-1}(x)[/tex]
[tex]f^{-1}(x) = x - 4[/tex]
Now, we can solve for [tex]f^{-1}(6)[/tex]
Substitute 6 for x
[tex]f^{-1}(6) = 6 - 4[/tex]
[tex]f^{-1}(6) = 2[/tex]
Help and show work plz
Answer:
RK: 4 and BC: 6
Step-by-step explanation:
SImilar triangles
find unknown / know sides
Which means (2x+2)/6 = (4x+2)/9
(X+1)/3 = (4x+2)/9
Multiply 9 to both sides
9/3 (x+1) = (4x+2)
3x+3 = 4x+2
1 = x
Answer: RK = 4, BC = 6
Step-by-step explanation:
In a similar triangle, the ratios of corresponding sides are the same. Thus, because of sides MK and AC, the triangles have a ratio of 6/9, or 2/3. Thus, you can determine that 2/3(4x+2)=2x+2.
Distribute
8/3x + 4/3 = 2x + 2
Subtract 2x
2/3x + 4/3 = 2
Subtract 4/3
2/3x=2/3
Divide by 2/3
x = 1
Then, simply plug-in 1 for x to get that RK is 4 and BC is 6
Hope it helps <3
Which set below is the domain of
{(2, -3),(-1,0), (0,4),(-1,5),(4, -2)}?
(AD {-3, 0, 4, 5, -2} (CD, {2,-1,4}
(3) -3,4,5,-2) (D) {2,-1,0,4}
Answer:
Domain { -1,0,2,4}
Step-by-step explanation:
{(2, -3),(-1,0), (0,4),(-1,5),(4, -2)}
The domain is the input values
Domain { 2,-1,0,-1,4}
We normally write them in order from smallest to largest and no repeating
Domain { -1,0,2,4}
Answer:
[tex]\large \boxed{\sf D. \ \{2,-1,0,4\}}[/tex]
Step-by-step explanation:
The domain are all possible values of x.
[tex]\{(2, -3),(-1,0), (0,4),(-1,5),(4, -2)\}[/tex]
The x values are 2, -1, 0, -1, and 4.
The domain of the set is {2,-1,0,4}.
PLEASE HELP!!! Will give brainliest to quickest CORRECT answer. No explanation needed :) Rebekah manages a yoga studio that charges each customer a one-time initial fee of $35 and an additional fee of $12 per class taken. Rebekah's goal is for each customer to spend at least $100 at the studio, and she wants to know the minimum number of classes a customer needs to take to meet that goal. Let C represent the number of classes a customer takes. 1) Which inequality describes this scenario? A. 35+C≤100 B. 35+3≥100 C. 35+12C≤100 D. 35+12C≥100 2) What is the minimum number of classes a customer can take for Rebekah to meet her goal?
The inequality that describes the scenario will be; 35 + 12C ≥ 100.
The minimum number of classes a customer can take for Rebekah to meet her goal is 6
What is inequality?Inequality is defined as the relation which makes a non-equal comparison between two given functions.
One-time initial fee = $35
Additional fee per class = $12
Minimum target = $100
Number of classes = C
One-time initial fee + (Additional fee per class) x (Number of classes) ≥ Minimum target
The inequality that describes the scenario will be;
35 + 12C ≥ 100
Then Solve for C to know the minimum number of classes a customer can take for Rebekah to meet her goal,
12C ≥ 100 - 35
12C ≥ 65
C ≥ 65 / 12
C ≥ 5.42
Thus, The minimum number of classes a customer can take for Rebekah to meet her goal is 6
Learn more about inequality ;
brainly.com/question/14164153
#SPJ2
Math Question (10 Points):
Answer:
0
Step-by-step explanation:
Like terms are terms that have the same variable part.
The variable part of all three terms is u, so all terms are like terms.
5u + u - 6u =
= 5u + 1u 6u
= 6u - 6u
= 0
which of these expressions are equivalent to p/3?
A. p-2/3
B. 1/3p
C. p-3
D. 3/p
E. 3p/p
This is assuming that p is not in the denominator. To make it more clear that p is not in the denominator, I recommend you write (1/3)p.
Taking 1/3 of a number is the same as dividing by 3.
Example:
27/3 = 9
27*(1/3) = 9
click to see equation, show work pls!
Answer:
x = 6, 9
Step 1:
To solve this equation, we need to subtract 3 from both sides like this:
[tex]3\sqrt{x-5} +3(-3)=x(-3)\\3\sqrt{x-5} =x-3[/tex]
Step 2:
We square both sides (multiply using FOIL) to get rid of the radical.
[tex](3\sqrt{x-5} )^2 = (x-3)^2\\(3\sqrt{x-5} )^2: 9x-45\\ (x-3)^2: x^2+6x+9\\\\9x-45=x^2-6x+9[/tex]
If you did not understand how these were done, here is an example:
(x + 1)(x + 2)
First terms: x * x = x^2
Outer terms: x * 2 = 2x
Inner terms: 1 * x = x
2x - x = x
Last terms: 1 * 2 = 2
x^2 + x + 2
Step 3:
Solve for x:
9x - 45 = x^2 - 6x + 9
x^2 - 6x + 9 (+45) = 9x - 45 (+45)
x^2 - 6x + 54 (-9x) = 9x (-9x)
x^2 - 15x + 54 = 0
Factor:
(x^2 - 6x) + (- 9x + 54)
x(x - 6) - 9(x - 6)
Factor out (x - 6):
(x - 6)(x - 9) = 0
x - 6 = 0; 6 - 6 = 0
x - 9 = 0; 9 - 9 = 0
Our anwer: x = 6, 9
A reduced scale drawing of a rectangle measures 12 inches by 16 inches. The scale factor is 1/4. What is the size of the original rectangle? A. 3 in. * 4 in. B. 16 in. * 20 in. C. 36 in. * 48 in. D. 48 in. * 64 in. Please show ALL work! <3
Answer: D) 48 inches by 64 inches
=============================================
Explanation:
The scale factor is 1/4 = 0.25, meaning that the original preimage is larger and it is reduced to get the image. The reduced width is 12, so the original width is 12/0.25 = 48 inches. The reduced length is 16 making the original to be 16/0.25 = 64.
--------
note that
48*0.25 = 12
64*0.25 = 16
showing how a 48 by 64 rectangle is reduced to a 12 by 16 rectangle after applying the scale factor to each dimension
Maria’s office is located at (–7,–5) on the coordinate plane. Her home is located at (4,–6) and the supermarket is located at (–2,–6). When returning back from the office, she first goes to the supermarket to buy some groceries, and then goes back home. Find the total distance she traveled from her office to home. A. 146−−−√+6 units B. 26−−√+6 units C. 82−−√+6 units D. 202−−−√+6 units
Answer:
B. 6 + √26
Step-by-step explanation:
1. Make a right triangle using the line that goes from office to supermarket.
2. Use pythagorean thereom to find the distance of the longest side.
3. FInd the distance of the line segment going from supermarket to Marias House.
4. Add them together to get 6 + √26.
Answer:
B.
Step-by-step explanation:
1. Make a right triangle using the line that goes from office to supermarket.
2. Use Pythagorean theorem to find the distance of the longest side.
3. Find the distance of the line segment going from supermarket to Maria's House.
4. Add them together to get 6 + √26.
A cylinder has a height of 4.5 cm and a diameter of 1.5 cm. What is the surface area of the cylinder in square centimeters? Use 3.14 for pi. A.21.2 B.24.7 C.7.9 D.31.8
Answer:
A = 56.5cm²
Step-by-step explanation:
r = 1.5cm
h = 4.5cm
A=2πrh+2πr2
A = 2πr(h+r)
A = 2 x 3.14 x 1.5 x ( 4.5 + 1.5 )
A = 56.62cm²
[tex] \large{ \underline{ \underline{ \bf{ \red{Given}}}}}[/tex]
Height of the cylinder = 4.5 cmDiameter of the cylinder = 1.5 cmConsider π = 3.14[tex] \large{ \underline{ \underline{ \bf{ \purple{To \: find}}}}}[/tex]
Surface area of the cylinder in cm²?[tex] \large{ \underline{ \underline{ \bf{ \green{Now, \: What \: to \: do?}}}}}[/tex]
For solving this question, we should know how to calculate the surface area of cylinder i.e Total surface are of cylinder = 2πr(r + h)
Where, r = radius of the cylinder and h is the height of the cylinder.
[tex] \large{ \bf{ \underline{ \underline{ \blue{Solution}}}}}[/tex]
We are provided with,
h = 4.5 cmd = 1.5 cmThen, Radius = 1.5 cm / 2
By using formula,
⇛ 2πr(r + h)
⇛ 2 × 3.14 × 1.5/2 (1.5/2 + 4.5) cm²
⇛ 2 × 3.14 × 3/4( 5.25) cm²
⇛ 24.7275 cm²
❇ Option B
✤ TSA of the cylinder = 24.7275 cm²
━━━━━━━━━━━━━━━━━━━━
please help real quick
Divide total km by the km in the scale:
112 / 16 = 7
The answer is A. 7 cm
Answer:
7 cm
Step-by-step explanation:
1 cm : 16 km :: x cm : 112 km
Product of mean = Product of extreme
16 * x = 1 * 112
x =[tex]\frac{112}{16}[/tex]
x = 7cm
What is the measure of the acute angle formed by the lines 3x–5y=–15 and 4x+2y=7?
Answer:
85.6 degrees.
Step-by-step explanation:
The given equations of lines are
[tex]3x-5y=-15[/tex]
[tex]4x+2y=7[/tex]
We need to find the measure of the acute angle formed by these lines.
[tex]Slope=\dfrac{-\text{Coefficient of }x}{\text{Coefficient of }y}[/tex]
Slope of given lines are
[tex]m_1=\dfrac{-3}{-5}=\dfrac{3}{5}[/tex]
[tex]m_2=\dfrac{-4}{2}=-2[/tex]
Angle between two lines is
[tex]\tan \theta = \left|\dfrac{m_1-m_2}{1+m_1m_2}\right|[/tex]
[tex]\tan \theta = \left|\dfrac{\dfrac{3}{5}-(-2)}{1+\dfrac{3}{5}(-2)}\right|[/tex]
[tex]\tan \theta = \left|\dfrac{\dfrac{3+10}{5}}{\dfrac{5-6}{5}}\right|[/tex]
[tex]\tan \theta = \left|\dfrac{13}{1}\right|[/tex]
[tex]\tan \theta = 13[/tex]
[tex]\theta = \tan^{-1}(13)[/tex]
[tex]\theta \approx 85.6^{\circ}<90^{\circ}[/tex]
Therefore, the acute angle between given lines is 85.6 degrees.
Plz help I’ll mark brainliest
Answer:
x = 22.62°Step-by-step explanation:
To find the measure of angle x we use cosine
[tex] \cos( \alpha ) = \frac{adjacent}{hypotenuse} [/tex]
From the question
PO is the hypotenuse = 13
The adjacent is 12
Substitute the values into the above formula
That's
[tex] \cos(x) = \frac{12}{13} [/tex]
[tex]x = \cos^{ - 1} ( \frac{12}{13} ) [/tex]
x = 22.6198
We have the final answer as
x = 22.62° to the nearest hundredthHope this helps you
Answer:
Since the value of all angles within a triangle must equal 180 degrees, if you know at least two angles, you can subtract them from 180 to find the missing third angle. If you are working with equilateral triangles, divide 180 by three to find the value of X. All of the angles of an equilateral triangle are equal.
Step-by-step explanation:
Kaitlin compared the statistics from her team's baseball season. She determined that having fewer hits did not imply that a player caught more or fewer balls. What should she conclude? a. There is no correlation between the number of hits and the number of balls caught. b. There is a correlation between the number of hits and the number of balls caught. There may or may not be causation. Further studies would have to be done to determine this. c.There is a correlation between number of hits and number of balls caught. However, there is no causation. This is because there is probably a decrease in the number of balls caught with a decrease in the number of hits.
Answer: c.There is a correlation between number of hits and number of balls caught. However, there is no causation. This is because there is probably a decrease in the number of balls caught with a decrease in the number of hits.
Step-by-step explanation:
Correlation is a term used to define a relationship between two variables.Causation is a term used to define the effect of one variable on other.Given, Kaitlin compared the statistics from her team's baseball season. She determined that having fewer hits did not imply that a player caught more or fewer balls.
There is a correlation between number of hits and number of balls caught. However, there is no causation as " fewer hits did not imply that a player caught more or fewer balls.".
This is because there is probably a decrease in the number of balls caught with a decrease in the number of hits.
Hence, the correct option is "c".
{(-2,8),(4,6),(10,4)} Which point, when added to the set, would form a relation that is not a function?
Answer:
Point : ( -2, 15 )
Step-by-step explanation:
A point that would make this relation not a function would be one that shares a common x - value with the other points. One common domain values for two range values would, when graphed, not follow the vertical test, hence making the relation not a function.
Let's say that the point is ( -2, 15 ). It has a common x - value with respect to the first point, ( -2, 8 ), and therefore would make this set not a function.
Answer:
Point : ( -2, 15 )
Step-by-step explanation:
Factorize. (i) 2mn +m^2-6n - 3m (ii) 4y^2 -81 (iii) t^2 - 6t+8
Answer:
(i) (m-3)(2n+m) (ii) (2y+9)(2y-9) (iii) (t-4)(t-2)
Step-by-step explanation:
2mn+m^2-6n-3m
m(2n+m)-3(2n+m)
(m-3)(2n+m)
Answer: (m-3)(2n+m)
------------------------------
4y^2-81
(2y+9)(2y-9)
Answer: (2y+9)(2y-9)
-------------------------------
t^2-6t+8
(t-4)(t-2)
Factors of the given equations are
(i) (2n +m)(m - 3)
(ii) (2y-9)(2y + 9)
(iii) (t -4) (t - 2)
What is factorization?" Factorization is the process of breaking down large number or quantity into a smaller number or quantity."
Formula used
(a² - b²) = (a -b) (a +b)
According to the question,
(i) 2mn + m² -6n -3m
= m (2n +m) - 3 (2n +m)
= (2n + m) (m - 3)
(ii) 4y² - 81
= (2y)² - (9)²
= (2y - 9) (2y + 9)
(iii) t² - 6t +8
= t² - 4t - 2t + 8
= t (t - 4) -2 (t - 4)
= (t -4) (t -2)
Hence, Factors of the given equations are
(i) (2n +m)(m - 3)
(ii) (2y-9)(2y + 9)
(iii) (t -4) (t - 2)
Learn more about factorization here
https://brainly.com/question/14067703
#SPJ2
plsss help meeeeeee!!!! Jakes club has 35 members. it's rules require that 60% of them must be present for any vote. at least how many members must be present to have a vote?
Answer:
21 members
Step-by-step explanation:
Jake's club
Total number of members = 35
percentage of members required to be present for any vote = 60%
= 60/100 × 35
= 0.6 × 35
= 21
What’s the mass of a liquid if its density is 0.95 G/ml and its volume is 200 ml
Answer:
190 g
Step-by-step explanation:
Mass =Density
Volume
Let the mass be x.
x/200=0.95
x=200 x 0.95
x = 190 g
Thank you!
Please help me on this question
Answer:
1st count the 1/2 circle with the formula
1/2 × phi × r²
=1/2 × 3,14 x 6²
=1/2 × 3,14 × 6²
=56,5
2st count the ractangle with the formhla
a × b
= 12 × 18
= 216
So we get 56,5+216= 272,5
Answer:
Hey there!
This problem will require a few steps to solve:
Step 1: Identify the "simple shapes" that make up the larger figure. Here, we see that there is a rectangle to the left, and a semicircle to the right.
Step 2: Find the area of the rectangle. This shouldn't be too hard, since we know that the formula for a rectangle's area is length times width. From the diagram, we have the length is 18cm, and the width is 12cm. 18 times 12=216.
Step 3: Find the area of the semicircle. This is slightly more difficult, but we know a semicircle is half of a circle, and the formula for circle area is [tex]\pi r^2[/tex]. Thus, the formula for a semicircle area is [tex]\frac{\pi r^2 }{2}[/tex]. We have d, or the diameter equal to 12, so the radius is 6, or half of the d. Plugging in the values, we find that the area for the semicircle is about 56.52.
Step 4: Add the areas of both simple shapes together: 216+56.52=272.52 cm^3.
Hope this helps :)
PLS HELP ME WITH THIS QUESTION, ANYTHING REALLY HELPSS!!!!
Answer:
x = 75
Step-by-step explanation:
FGE is a straight line so it equals 180 degrees
FGA + AGC + CGE = FGE
x + 90 + 15 = 180
Combine like terms
x+ 105 = 180
Subtract 105 from each side
x = 180-105
x = 75
Answer:
x = 75º
Step-by-step explanation:
The Vertical Angle Theorem shows that:
∠CGE ≅ ∠DGF
So:
∠DGF = 15º
∠AGD = 90º
90º - 15º = 75º
x = 75º
solve the equation
[tex] {5}^{n + 1} - {5}^{n} + {5}^{n - 1} = 105[/tex]
Answer:
n=2
Step-by-step explanation:
Hello, please consider the following.
[tex]{5}^{n + 1} - {5}^{n} + {5}^{n - 1} = 105\\\\5^{n-1}(5^2-5+1)=5^{n-1}(25-5+1)=21*5^{n-1}=105\\\\5^{n-1}=\dfrac{105}{21}=5=5^1\\\\\text{It means that}\\\\n-1=1 <=> n=2[/tex]
Let me know if you need more details.
Thank you
