Question

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

Answer 1

To first find the sum, we may need to find the common ratio of this sequence.

It is -2.

Now we just have to plug in the geometric series formula:

(-4(1-(-2)^7))/(1+2)

= (-4(1-(-128))/3

=(-4)(129)/3

= -172


So the sum of the first 7 terms are -172


Hope this helps!