Factor
Factor: "any of the numbers or symbols in mathematics that when multiplied together form a product" (2012).

When factoring a binomial expression you first multiply the beginning constant with the last constant of the equation. This is the number that the factors will multiply to equal. Then the middle constant of the binomial is what the two numbers will add to equal.
For example: Let f(x)=x^2+3x+2 We know that 1*2=2 and that our middle constant is 3. Now think of two numbers that multiply together to equal 2 and add together to equal 3... 1 and 2, right? So then we write out our two factors like this: f(x)=(x+1)(x+2)=0. We can check our answer by using the foil method and see if we get back to the origional equation.