Question

Identify the errors made in finding the inverse of y = x2 + 12x.

Answer 1

The student did not switch both instances of x with y. He should have written x = y2 + 12y.He wrote only the principal square root instead of using the ± sign.The domain is incorrect. For the radicand to be greater than or equal to zero, x must be less than or equal to zero. It should be x < 0.

Answer 2

The first error was made when the variables were changed, the x in 12x was not changed to y.
The second error was when the square root of -11x was taken, for -11x to be positive x should be less than 0 not greater or equal to 0.