Four different integers form an increasing A.P. One of these numbers is equal to the sum of the squares of the other three numbers. Find the numbers
My Attempt:
I assumed the four numbers as: $(a-3d), (a-d), (a+d), (a+3d)$ but now i can't understand which number to square.
Hint: Clearly the largest number must be the sum of the square of the other three. Otherwise, the square of the largest one would be in the sum, and the square of the largest one, plus other stuff, is larger than any of the other terms.