Question

The sum of the series –2, 6, –18, …. to 7 terms is​

Answer 1

Formula used

$s(n) = \frac{a(1 - r {}^{n}) }{1 - r}$

Given,

n=7

a=-2

r=6/-2=-3

Therefore

$s(7) = \frac{ - 2(1 - ( - 3) {}^{7} )}{1 - ( - 3)} \\ = \frac{ - 2 \times2188 }{4} \\ = - 1094$

Answer

Sum is =-1094