How do you factor $x^2-7x-18$ ?

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Answer 1 · 2016-11-30T04:34:29

$(x - 9)(x + 2)$

First step, we need to split the equation up into factors that will multiply back into the given quadratic.

What times $x$ will yield $x^2$ ?

$x * x$ , of course.

So, that gives us factors of $x^2$

$(x" ")(x" ")$

Now we need two numbers that will multiply into $-18$ and subtract into $-7$ .

The factors of $18$ are $2,3,6,9$ .

$(-9)(+2) = -18 " "$ and $" " -9 + 2 = -7$

Therefore

$= x^2-7-18$

$= (x -9)(x+2)$

Always look for the operator signs as a helping indicator.

Hope this helps.

How do you factor x^2-7x-18x^2-7x-18?