# Precalculus

posted by
**Laura**
.

Find the sum of 20 (summation notation symbol)k=1 then (3k-5)

If you mean the sum of the first 20 terms, beginning with k=1, of

ak = 3k - 5,

that would be -20 x 5 = -100

PLUS the sum of the first 20 terms of

ak = 3k

The latter is 3 times the sum of

1+2+3+...20 ,

or 3*(20)(21)/2= 630

So the answer is 630 - 100 = 530