How do you factor $x^2 - x - 12?$ ?

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Answer 1 · 2015-05-03T07:33:27

We can Split the Middle Term of this expression to factorise it

In this technique, if we have to factorise an expression like $ax^2 + bx + c$ , we need to think of 2 numbers such that:

$N_1*N_2 = a*c = 1*-12 = -12$
AND
$N_1 +N_2 = b = -1$

After trying out a few numbers we get $N_1 = 3$ and $N_2 =-4$

$3*-4 = -12$ , and $3+(-4)= -1$

$x^2 - x - 12 = x^2 +3x - 4x - 12$

$= x(x+3) - 4(x+3)$

$x+3$ is a common factor to each of the terms

$=color(green)((x+3)(x-4)$

How do you factor x^2 - x - 12?x^2 - x - 12??