If we write:

(a+b)²

it means:

(a+b)(a+b)

however, if I want to mean the square of the sum, how would I write it algebraically?

What's wrong with (a+b)², isn't that the square of the sum of a and b?

I don't understand the question.

a + b = sum_ab

sum_ab^{2 =} (a + b)² = (a + b)(a + b)

----

Or with numbers to show an example:

Yes, it is equivalent, what an idiot of me...

Yes, it is equivalent, what an idiot of me...

(a+b)² is square of the sums, perhaps you were confusing it with the sum of the squares, (a² + b²), ala pythagoras'?

Actually I meant square of the sum.