How do you solve 3x^2 - 15x + 18 = 0 3x215x+18=0 using the quadratic formula?

1 Answer
Jul 10, 2016

The answers are x = 2, 3x=2,3.

Explanation:

The quadratic formula is:

x = (-b +- sqrt(b^2 - 4ac))/2ax=b±b24ac2a

And in your polynomial:
a = 3a=3
b = -15b=15
c = 18c=18

So plugging those in we get:

x = (15 +- sqrt(15^2 - 4*3*18))/(2*3)x=15±152431823
= (15 +- sqrt(225 - 216))/6=15±2252166
= (15 +- sqrt(9))/6=15±96
= (15 +- 3)/6=15±36

So our two answers are:

x = (15 - 3)/6 = 12/6 = 2x=1536=126=2
and
x = (15 + 3)/6 = 18/6 = 3x=15+36=186=3