Question 805062
x^2 + 2xy + y^2 - a^2 - 2ab - b^2


{{{(x^2 + 2xy + y^2) - (a^2 + 2ab + b^2)}}}


{{{(x+y)^2-(a+b)^2}}}

difference of two squares


{{{(x+y+a+b)(x+y-a-b)}}}