x= √(54-3x)
square both sides:
x^2=54-3x
bring everything to the left:
x^2 + 3x - 54= 0
solve using quadratic formula:
x= (-3 +/- √(9- 4(-54)))/2=
(-3+/- √(9+216))/2=
(-3 +/- √225/2=
(-3 +/- 15)/2=
two options:
1) x= (-3+15)/2= 12/2=6
2) x= (-3-13)/2= -18/2= -9
