Solve the Quadratic Equation: -x² - 7x - 12 = 0

Question

Solve for x.

$-x^2-7x-12=0$

00:00 Solve

00:03 Multiply the entire exercise by minus to make it positive

00:15 Use trinomial to find the solution

00:19 Find 2 numbers whose product equals value C

00:23 And their sum equals value B

00:35 These are the matching numbers

00:45 Substitute these numbers in the trinomial

00:50 Find what zeros each factor

00:54 Isolate the unknown, this is one solution, now let's find the second

01:02 And this is the solution to the question

First, factor using trinomials and remember that there might be more than one solution for the value of $x$ :

$-x^2-7x-12=0$

Divide by -1:

$x^2+7x+12=0$

$(x+3)(x+4)=0$

Therefore:

$x+4=0$

$x=-4$

Or:

$x+3=0$

$x=-3$

$x=-3,x=-4$