Question

Find three numbers in A.P whose sum is 21 and the product of last two numbers is 63.

Answer 1

Let, the three numbers be a-d,a,a+d

Given, a-d+a+a+d=21

3a=21

Therefore,a=7........<1>

Given, a(a+d)=63

a^2+ad=63

From<1>,

49+7d=63

7d=14

d=2.....<2>

Thus , required three terms of an AP are (7-2),7,(7+2) =5,7,9...

Hope it helps you...