homework help?

Question

show that 4+2+0+.............+12 terms = -84

Answer 1

It looks like you've started an arithmetic series, where each term is 2 less than the previous one:

4 + 2 + 0 - 2 - 4 - 6 - 8 - 10 - 12 - 14 - ...

There is a formula for the sum of the first n terms of an arithmetic series:

S = (n/2)(2*a_1+d(n-1))

where n is the number of terms, a_1 is the first term, and d is common difference. So in our case the sum is

S = (12/2)(2*4 + (-2)(12-1)) = 6(8-22) = 6(-14) = -84

Answer 2

-84-12-4-2-0= -66