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

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Answer 1 · 2018-03-02T09:15:25

See below...

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.