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Special factoring formulae to memorize

Let's look at a few formulae you'll encounter quite often in special factoring. The first three are the inverse of the formulae we looked at in our last article, and the two following that are relatively new. Since they will be encountered often in your work on factoring, it will be helpful, like our previous formulae, to memorize these:

x^2 + 2ax + a^2 = (x + a)^2

x^2 - a^2 = (x + a)(x - a)

x^2 + (a +b)x + ab = (x + a)(x + b)

x^3 - a^3 = (x - a)(x^2 + ax +a^2)

x^3 + a^3 = (x +a)(x^2 - ax +a^2)