Question

The 24th term of an A. P is twice it's 10th term. Show that it's 72nd term is 4times it's 15th term

Answer 1

t24=2t10

a+23d=2a+18d

23d-18d=2a-a

a=5d

t72= a+71d=5d+71d=76d

t15=a+14d=5d+14d=19d

76d=4(19d)

t72=4×t15