How do you solve $2x^2 + x - 1=0$ by factoring?

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Answer 1 · 2015-08-17T06:29:28

The solutions are
$color(blue)(x=-1,x=1/2$

$2x^2+x−1=0$

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:

$N_1*N_2 = a*c = 2*-1 = -2$
AND
$N_1 +N_2 = b = 1$

After trying out a few numbers we get $N_1 = 2$ and $N_2 =-1$
$2*-1 = -2$ , and $2+(-1)= 1$

$2x^2+x−1=2x^2+2x-1x−1$

$2x(x+1) -1(x+1)=0$

$(2x-1)(x+1)=0$
Now we equate the factors to zero
$2x-1=0, color(blue)(x=1/2$
$x+1=0, color(blue)(x=-1$

How do you solve 2x^2 + x - 1=02x^2 + x - 1=0 by factoring?