Question

I REALLY NEED HELP!!!

Jose knows that the equation y = |x| + 4 is a function. He concludes that all equations that include absolute values are functions. Which equation shows that Jose's conclusion is not correct?

A. x = y + |-4|
B. y = |x + 4|
C. x = 4 - |y|
D. y = |-×| + 4

Answer 1

D. y= |-x| + 4 is the answer

Answer 2

C. because y can be either positive or negative and by definition for any point x, there can only be one value for y. It fails what they call the vertical line test. In other words:

f(x) can have only one y value for any given value of x, otherwise it is not a function.