Question

How do you solve quadratic equation: `x^2+2x-8` by factoring?

Answer 1

`x = 2 or x =-4`

Explanation:

There is a contradiction in the question.

It is an expression, not an equation, so it cannot be solved.
However, let's assume it was supposed to read as

`x^2 +2x-8 = 0" make a quadratic equation equal to 0"`

Find the factors.
Reading from the back we have the following information.

"Find the factors of 8 which subtract (-) to make 2".
"The signs will be different (because of -)"
"There must be more positives. (because of +2)"

Factors of 8 are either 8 x 1 or 4 x 2 .

4-2 = 2 , so these are the factors we want.

Write the factors in the brackets: `(x" "4)(x" "2) =0`

Fill in the signs: `(x + 4)(x - 2) =0" "4>2, 4 " is positive"`

Now because the answer is 0, each bracket could be 0.

If `x+4 = 0" "rArr x =-4`

If `x-2 = 0" "rArr x =2`

These are the solutions to the equation.