Find the sum of the convergent series 4-2+1-1/2

[vipertongn]

find the sum of the convergent series 4-2+1-1/2 ...

Homework Statement

find the sum of the convergent series . 4-2+1-1/2...

Homework Equations

sum of r^n |r|< 1 --> 1/(1-r)= sum

The Attempt at a Solution

4(1-1/2+1/4-1/8...)
I can see a pattern here where the denominator is going 2,4,8 so its like 1*2, 2*2, 2*2*2 but the 1 and + and the - throws me off...can someoen help me?

 

[Tedjn]

If this in fact is a geometric series, what would the common ratio be?

 

[Cyosis]

Hint: incorporate $(-1)^n$ to solve your sign problem.