Question

sum of 3 terms of an a.p is 30 and sum of square of extremes is 250.find the terms and sum of 20 terms

Answer 1

let the 3 terms are a - d , a and a+d

now a - d + a + a + d =30

a = 10

now (a-d)^2 + (a+d)^2 = 250

2a^2 + 2d^2 = 250

2 * 10*10 + 2d^2 = 250

d^2 = 25

d = 5

now sum of 20 terms

20/2(2*10 + 19*5)

1150