Question

Which of the following is an extraneous solution

Answer 1

Answer:

3 or

C

Step-by-step 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