How do you solve #-5x ^ { 2} - 3x + 8= 0#?

1 Answer
Nov 13, 2017

See a solution process below:

Explanation:

We can use the quadratic equation to solve this problem:

The quadratic formula states:

For #color(red)(a)x^2 + color(blue)(b)x + color(green)(c) = 0#, the values of #x# which are the solutions to the equation are given by:

#x = (-color(blue)(b) +- sqrt(color(blue)(b)^2 - (4color(red)(a)color(green)(c))))/(2 * color(red)(a))#

Substituting:

#color(red)(-5)# for #color(red)(a)#

#color(blue)(-3)# for #color(blue)(b)#

#color(green)(8)# for #color(green)(c)# gives:

#x = (-color(blue)(-3) +- sqrt(color(blue)(-3)^2 - (4 * color(red)(-5) * color(green)(8))))/(2 * color(red)(-5))#

#x = (3 +- sqrt(9 - (-160)))/-10#

#x = (3 +- sqrt(9 + 160))/-10#

#x = (3 +- sqrt(169))/-10#

#x = (3 - 13)/-10# and #x = (3 + 13)/-10#

#x = (-10)/-10# and #x = 16/-10#

#x = 1# and #x = -8/5#