19. Let   f(x) = 3x + 4.   Find   f -1(x).   Graph both   f   and   f -1   in the same coordinate system.

Let y = 3x + 4 and solve for x

y - 4 = 3x

So

thus

For the graph,   f(x)   has a slope of   3   and a y-intercept of   4.   f -1(x)   has a slope of  1/3   and a y-intercept of   4/3.

Not that the graph of   f-1(x)   is the reflection of the graph of   f(x)   about the line   y = x.