4) For the sum -10 -13 -16 -... -43:

(a) Rewrite the sum using summation notation (\(\sum\)).

(b) Evaluate the sum.

(a)

12

∑ -7 - 3n

n = 1

Note that other forms are possible.....

(b) The sum can be found as

[ First Term + Last Term ] * [ Number of terms] / 2

The number of terms is [ 43 - 10 ] / 3 + 1 = 33/3 + 1 = 11 + 1 = 12

So....the sum is

[ -10 + -43 ] * [ 12 / 2] =

] -53] * 6 =

-318