This applet allows for a quick graphical check whether a function will have an inverse. The reflection of your f(x) is shown in red. Use the vertical line test to determine if the reflection is a function. If the reflection is not a function then your f(x) is not invertible.
Use the applet to determine if the functions [math]f(x)=x^2+1[/math], [math]g(x)=2x+3[/math], [math]h(x)=(2x+8)^3[/math], and [math]j(x)=\sqrt{x}[/math] are invertible.