How do you factor $x^2 +3x - 18 = 0$ ?

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Answer 1 · 2015-05-23T09:20:52

$x^2 + 3x -18$

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:

$N_1*N_2 = a*c = 1*(-18) = -18$
and,
$N_1 +N_2 = b = 3$

After trying out a few numbers we get $N_1 = 6$ and $N_2 =-3$
$6*(-3) = -18$ and $6+(-3)= 3$

$x^2 + 3x -18 = x^2 + 6x - 3x -18$

$x(x+6) -3(x+6)$

$color(green)((x-3)color(red)((x + 6)$ is the factorised form.

How do you factor x^2 +3x - 18 = 0x^2 +3x - 18 = 0?