SOLUTION: Solve (-3x+18)^(1/2) = x

Algebra ->  Rational-functions -> SOLUTION: Solve (-3x+18)^(1/2) = x      Log On


   

Question 603673: Solve (-3x+18)^(1/2) = x
Answer by alicealc(293) About Me  (Show Source):
You can put this solution on YOUR website!
%28-3x%2B18%29%5E%281%2F2%29+=+x
sqrt%28-3x%2B18%29+=+x
square both sides:
-3x+%2B+18+=+x%5E2
0+=+x%5E2+%2B+3x+-+18
0+=+%28x+%2B+6%29%2A%28x+-+3%29
x + 6 = 0 or x - 3 = 0
x = -6 or x = 3

if -6 is substituted into the equation, it will be:
sqrt%28-3%2A%28-6%29%2B18%29+=+-6
sqrt%2836%29+=+-6
we got wrong answer

but, if 3 is substituted into the equation, it will be:
sqrt%28-3%2A3%2B18%29+=+3
sqrt%289%29+=+3
the answer is right

so, the solution for x is 3