How do you factor completely $x^2 + 2x – 15$ ?

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Answer 1 · 2018-03-02T09:15:25

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To factorise, we firstly need two brackets, each containing an $x$ .

$(x )(x )$

This creates the $x^2$ term.

Now we need to get the rest of the terms. To do this, we need two factors of $-15$ which will add/subtract to give us $+2$

The two factors that do this are $-3$ and $5$ , as $-3+5 = 2$

$therefore (x-3)(x+5)$

You can check by expanding it out.

When looking for factors, if it is not obvious straight away then list them out and you'll eventually get there.

How do you factor completely x^2 + 2x – 15x^2 + 2x – 15?