# Square of a Sum

How to solve the square of a sum problems: formula, examples, and their solutions.

## Formula

(*a* + *b*)^{2} = (*a* + *b*)(*a* + *b*).

By using the FOIL method,

(*a* + *b*)(*a* + *b*) = *a*^{2} + 2*ab* + *b*^{2}.

So (*a* + *b*)^{2} = *a*^{2} + 2*ab* + *b*^{2}.

See the brown (+) signs.

The (+) sign in (*a* + *b*)^{2}

makes the middle term (+): +2*ab*.

It's the difference between

this formula and (*a* - *b*)^{2} formula.

## Example 1

Put *x*, (+), 3 into the formula.

## Example 2

Put 2*m*, (+), 5*n* into the formula.