Question

Solve for x x squared plus 4X minus 21 equals 0

Answer 1

x = -7 and x = 3

Explanation:

x² + 4x - 21 = 0 factors as follows: (x + 7)(x - 3) = 0.

Then x = -7 and x = 3.

Answer 2

`x = 3\\x = -7`

Explanation:

We have the following quadratic equation

`x^2 + 4x - 21 =0`

To solve the equation we must factor it.

To factor the equation we must find 2 numbers b and c that when adding them, you obtain as result 4 (
`c + b = 4`) and when multiplying them, you obtain as result -21 (
`c * b = -21`).

Then the polynomial will be factored in the following way:

`(x+c)(x + b) = 0`

You can verify that the numbers that meet this condition are:
`b = 7\\c = -3`

So

`x^2 + 4x - 21 =(x-3)(x + 7)=0`

Finally the solutions are:

`x = 3\\x = -7`