An expression of the form a^2+2ab+b^2 can be factored to a perfect square. a^2+2ab+b^2=(a+b)^2 An example is the expression x^2+10x+25 which can be written as x^2+2* x * 5+5^2, and thus, be factored to the square of the binomial x+5. x^2+2* x * 5+5^2=(x+5)^2