Exercise 20 Page 125

Usually, when we think about points on coordinate planes, we think of them as x-coordinates and y-coordinates. However, when we use function notation, we use f(x) instead of y. ( x, y) ⇔ ( x, f(x)) We want to know the value of x when f(x)=7. To do this, we need to find the corresponding x-value of the function when the y-value is 7.

We can see that the function crosses through the point (-3,7). Therefore, when f(x)=7, x=-3.