Question

find the sum of the first ten terms of an ap. whose fourth term is 13and eigth term is 29​

Answer 1

Answer:

190

Step-by-step explanation:

An=a+(n-1)*d

A4=a+(4-1)*d

13=a+3d---------(1)

and

A8=a+(8-1)*d

29=a+7d--------(2)

from 1and 2

a+3d=13

a+7d=29

---------------

-4d=-16

d=16/4=4

and

a+3*4=13

a=1

So sum of first ten terms

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

S10=10/2[2*1+(10-1)*4]

=5*[2+9*4]

=5*38

=190

I think it is helpful for you