Question

how many terms of AP 8,15,22,.... add upto 1490

Answer 1

Given:

a=8.

d=15-8=7.

S=1490

S=n/2*[2a+(n-1)d]

1490=n/2*[16+7n-7]

=2980=n*[9+7n]

7n²+9n-2980=0

=7n²-140n+149n-2980=0

=7n(n-20)+149(n-20)=0

=(7n+149)(n-20)=0

Either

7n=-149

=n=-149/7

but n cannot be negative

so n-20=0

n=20.

The answer is 20 terms.

Hope it helps you.

Answer 2

Step-by-step explanation:

right this musch only your answer will right