Question

Which function has an inverse that is a function?

Answer 1

1. y = x^2 +3 
x = y^2 +3
x - 3 = y^2
y = + or - √(x-3) not a fction

2. y = 0x -9
x = 0y -9
x = -9 not a fction

3. y = -7x
x = - 7 y 
y = - x/7 yes function

4. y = |x|
x = |y|
y= x,-x not a function