How do you solve $x^2+5x-84=0$ using the quadratic formula?

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Answer 1 · 2015-08-10T07:48:06

The solutions for the equation are:
$color(blue)(x=7$ , $color(blue)(x=-12$

$x^2+5x−84=0$

The equation is of the form $color(blue)(ax^2+bx+c=0$ where:
$a=1, b=5, c=-84$

The Discriminant is given by:
$Delta=b^2-4*a*c$

$= (5)^2-(4*1*(-84))$

$= 25 + 336 = 361$

The solutions are found using the formula:

$x=(-b+-sqrtDelta)/(2*a)$

$x = ((-5)+-sqrt(361))/(2*1) = ((-5+-19))/2$

The solutions are:
$x= ((-5+19))/2 = 14/2 , color(blue)(x=7$

$x= ((-5-19))/2 =-24/2, color(blue)(x=-12$

How do you solve x^2+5x-84=0x^2+5x-84=0 using the quadratic formula?