Question

The last term of an ap 2,5,8,11 is x.the sum of terms of ap is 155.find the value of x

Answer 1

Answer:

Sn= n÷2(2a+(n-1)d)

155=n÷2(2×2+(n-1)3)

155=n÷2(3n+1)

310=3n^2+n

3n^2+n-310

by solving we get

n=10

then last term =

a+ (n-1)d= 2+(10-1)3=

2+27=29

Step-by-step explanation:

Answer 2

Answer: Sn=n/2(2a+(n-1)d => 155=n/2(3n+1) =>310=3n^2+n =>n=10. Now the last term is a+(n-1)d =2+9×3=29