find four numbers in AP whose sum is 20 and sum of whose squares is 120

four numbers in A.P. be

a-3d,a-d,a+d,a+3d..(imp step)

Acc to question,

a-3d+a-d+a+d+a+3d=20

So,

4a=20

a=5

Next,

 sum of the squares of these numbers =120 (given)

So, the A.P. is

2,4,6,8 (with d=1)

or

8,6,4,2 (with d=-1)