Question

Find the indicated sum. Show your work. ? (refer to image)

Answer 1

`2`

Explanation:

`sum_(k=1)^(4)(-1)^k(k+11)`

This sum can be computed as:
`sum_(k=1)^(4)(-1)^k(k+11)=(-1)^1(1+11)+(-1)^2(2+11)+(-1)^3(3+11)+(-1)^4(4+11)=`

`sum_(k=1)^(4)(-1)^k(k+11)=-12+13-14+15= 2`