Answer:
3 or
C
Explanation:
(45 - 3x)^1/2 = x - 9 Square both sides
45 - 3x = x^2 - 18x + 81 Switch sides
x^2 - 18x + 81 = 45 - 3x Add 3x to both sides
x^2 - 15x + 81 = 45 Subtract 45 from both sides
x^2 - 15x + 36 = 0 Factor
(x - 12)(x - 3) =0
The answers are
x = 12
x = 3
Now the question asks which is extraneous. The answer will be which ever number won't solve the original equation. Looking at it right now, both look OK.
(45 - 3*12)^1/2 = 12 - 9
(45 - 36)^1/2 = 3
(9)^1/2 = 3
So 12 is a proper solution.
What about 3?
(45 - 3*3)^1/2 = 12 - 3
(45 - 9)^1/2 = 9
36^1/2 = 9
6 does not = 9
The extraneous solution is x = 3