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

Question

5043 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-07-10T15:45:41

The answers are #x = 2, 3#.

#x = (-b +- sqrt(b^2 - 4ac))/2a#

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

So plugging those in we get:

#x = (15 +- sqrt(15^2 - 4*3*18))/(2*3)#
#= (15 +- sqrt(225 - 216))/6#
#= (15 +- sqrt(9))/6#
#= (15 +- 3)/6#

So our two answers are:

#x = (15 - 3)/6 = 12/6 = 2#
and
#x = (15 + 3)/6 = 18/6 = 3#