Find the four numbers in A.P. whose sum is 20 and the sum of whose squares is 120.

Explanation

To find the four numbers in Arithmetic Progression (A.P.) whose sum is 20 and the sum of whose squares is 120, we can follow these steps:

### Step 1: Define the terms of A.P.
Let the four numbers in A.P. be:
- \( a - 3d \)
- \( a - d \)
- \( a + d \)
- \( a + 3d \)
...