Question

What is the sum of the first 7 terms of the series −4+8−16+32−... ?

Answer 1

we have that

−4+8−16+32−.....

a1=-2*(-2)-----> -4

a2=-4*(-2)-----> +8

a3=+8*(-2)-----> -16

a4=-16*(-2)----> +32

a5=+32*(-2)----> -64

a6=-64*(-2)-----> +128

a7=+128*(-2)-----> -256

The sum of the first 7 terms of the series is

[a1+a2+a3+a4+a5+a6+a7]-----> [-4+8-16+32-64+128-256]-------> -172

the answer is -172