# What is this technique called?

It's been a long time since I've done algebra. I remember how to do it, but I'm at a loss to explain it. For instance, my son has the following problem; $$\frac{3}{Q+1}+\frac{2}{Q}$$ So I say, you just have to find a common denominator (like when you add "regular" fractions). All you need to do is this; $$\color{red}{\frac{Q}{Q}}\frac{3}{Q+1}+\frac{2}{Q}\color{red}{\frac{Q+1}{Q+1}}$$ What is this called?

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