Which function has an inverse that is also a function? g(x) = 2x – 3 k(x) = –9x2 f(x) = |x + 2| w(x) = –20

G(x) = 2x - 3 has a linear inverse which is a function.

k(x) = -9x2 has a square root inverse that is a function on only the interval x < 0.

Step-by-step explanation:

The inverse of a function is a reflection across the y=x line. This results in switching the values of the input and output or (x,y) points to become (y,x). This can be done algebraically in an equation as well. Begin by switching the x and y in the equation then solve for y.

x = 2y - 3 > y = x/2 + 3/2 is linear and a function.

-9y2 = x > y = √(-x/9)  is a square root that is a function on only the interval x < 0.

Absolute value does not have an inverse function.

x = -20 is a vertical line which is not a function.