$(X + Y)2=X2+ 2XY + Y2$

This formula is one of the shortcut formulas and it describes the square sum of two numbers.

That is, when we encounter two numbers with a plus sign (sum) and they are between parentheses and raised as an expression to the square, we can use this formula.

**Pay attention** - The formula also works for non-algebraic expressions or combined combinations with numbers and unknowns.

It's good to know that it is very similar to the formula for the difference of squares and differs only in the minus sign of the central element.