Question

-7+12-17+22-27
What is a possible expression for the series

Answer 1

just x-17 because you just reduce this in the calculator

Answer 2

Signs start with a negative and alternate, so the general term will have (-1)^n as a factor. The common difference has a magnitude of 5, so the general term is

`a_(n)=(-1)^(n)\cdot (7+5(n-1))`

and the sum is

`\displaystyle S=\sum_(n=1)^(5){(-1)^(n)\cdot (5n+2)}=-17`