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.