How do you solve 3x^2 + 11x – 20 = 0 using the quadratic formula?

1 Answer
Jul 27, 2018

x=4/3 and x=-5

Explanation:

We know that the quadratic formula is (-color(blue)(b)+-sqrt(color(blue)(b)^2-4color(red)(a)color(green)(c)))/(2color(red)(a)).
All we need to do is extract the values for color(red)(a), color(blue)(b), and color(green)(c) from the equation.

color(red)(3)x^2+color(blue)(11)xcolor(green)(-20)

We can see that:
color(red)(a)=color(red)(3
color(blue)(b)=color(blue)(11
color(green)(c)=color(green)(-20

Now, we can just plug those values into the quadratic formula:

(-color(blue)(11)+-sqrt(color(blue)(11)^2-4color(red)((3))color(green)((-20))))/(2color(red)((3)))

(-11+-sqrt(121+240))/(6)

(-11+-sqrt(361))/6

(-11+-19)/6, which is

(-11+19)/6 and (-11-19)/6, which is

8/6 and -30/6, which is

4/3 and -5.

These are the solutions to the equation above.