The differnce of 2 perfect cubes
remember
a³-b³=(a-b)(a²+ab+b²)
so
First, we need to solve for the common ratio from the data given by using the equation.
a(n) = a(1) r^(n-1)
15 = -3 r^(2-1)
-5 = r
r = -5
Then, we can find the sum by the expression:
S(n) = a(1) ( 1 - r^n) / 1-r
S(8) = -3 (1 + 5^8) / 1+5
S(8) = -195313
Elga's age = x
Alvin's age = x + 7
x + x + 7 = 97.
Simplify the left side of the equation
2x + 7 = 97.
Subtract 7 from each side
2x = 90.
Divide each side by 2
x = 45
Since x is equal to Elga's age, Elga is 45 years old
Answer:
38260
Step-by-step explanation:
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