How do you factor the expression $x^2 + 2x - 15$ ?

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Answer 1 · 2016-03-16T12:46:42

$(x -3) (x+5)$ is the factorised form of the expression.

$x^2 + 2x -15$

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:

$N_1*N_2 = a*c = 1*(-15) = -15$

AND

$N_1 +N_2 = b = 2$

After trying out a few numbers we get $N_1 = 5$ and $N_2 =-3$

$5*(-3) = -15$ , and $5+(-3)= 2$

$x^2 + 2x -15 = x^2 + 5x - 3x -15$

$= x (x+5) - 3(x+5)$

$= (x -3) (x+5)$ .
$(x -3) (x+5)$ is the factorised form of the expression.

How do you factor the expression x^2 + 2x - 15x^2 + 2x - 15?