Question

The sun of first and 5th term of ascending is ap is 26 and product of 2nd and 4th term is 160. Find sum of first 7 terms of a.p

Answer 1

• a+a+4d=26

2a+4d=26

a=13-2d equa 1

• (a+d)*(a+3d)=160 equa 2

a,a+d,a+2d,a+3d, a+ 4d,a+ 5d,a+6d=?

• putting this value in equa 2

(13-2d+d)*(13-2d+3d)=160

(13-d)*(13+d)=160

13^2-d^2 =160

d=3

• putting in equa1

a=13-2(3)

a=13-6

a=7

a, a+ d, a+ 2d, a+ 3d, a+ 4d, a+ 5d , a+6d = ?

sum of first 7 terms:

7+7+3+7+6+7+9+7+12+7+15+7+18=112