Question

What is the sum of the first 7 terms of the series −8+16−32+64−... ?

Answer 1

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Answer 2

Answer:

The sum of first 7 terms of the series is -344.

Step-by-step explanation:

The given series is  −8+16−32+64−...

It represents a GP with first term a = -8 and common ratio r = -2

We have to find the sum of first 7 terms. Hence, n = 7

The formula for the sum of n term of a GP is given by

$S=\frac{a(1-r^n)}{1-r}\\\\S=\frac{-8(1-(-2)^7)}{1-(-2)}\\\\S=-\frac{1032}{3}\\\\S=-344$

Hence, the sum of first 7 terms of the series is -344.