Question

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

Answer 1

Answer:

x = -7 and x = 3

Step-by-step explanation:

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

Then x = -7 and x = 3.

Answer 2

Answer:

$x = 3\\x = -7$

Step-by-step 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:

$x = 3\\x = -7$