Which of the following equations is not a one-to-one function?

Question

Which of the following equations is not a one-to-one function?

A.  y = x

B. y = x² + 3

C. y = x − 3

D y = x³

Answer 1

B. y = x² + 3 (it is possible to have one y value map to two x values in a quadratic therefore not one to one)

Example:

When y = 12,

12 = x² + 3

9 = x²

x = 3 or -3