1) Gathering the data
2) Simplifying the expression. The use of brackets and parentheses is to avoid confusion.
(a+b)² = a² +2ab +b² The square of the sum
2( m . n ) - [(m+n)²]= Setting the expression
2mn -[m² +2mn +n²] Place the minus outside since it is subtracting
2mn -m² - 2mn -n² Cancel out the opposite terms
-m² -n² Simplest form.
Or we can just let it factored.
2 mn - (m+n)²