Extra #4

When we described how to evaluate a function, we said that we could plug in an input and get out an output. For instance, if we wanted to evaluate f(x) = 2x + 1 at x=5, we can plug a 5 in and get an 11 out. Would it be possible to evaluate a function if we were only given a graph of it?

The picture above is a graph of the function f(x) = (-1/2)x +4. We can evaluate the function for x = -4 without doing any math. All we need to do is locate -4 on the x-axis, and see where the line is at that point. At x = -4, the corresponding y-value is 6. This means f(-4) = 6.