Hello, sheryl!

I know a proof for a similar problem, but I've hit a wall.

Let me show you the groundwork . . . maybe you can finish it.

The product of four positive integers in arithmetic progression

cannot be the square of an integer.

Let the four numbers be: .

Suppose their productisa square.

Then we have: .

Regroup: .

Multiply: .

And we have: .

Multiply: .

And this issupposedto lead to a contradiction . . . but I can't find it.

Anyone? .Anyone?