For a function shown as a graph, function evaluation means finding the output for the input inside the parentheses. Find that input on the horizontal axis, then read the curve's height. If the input is , you're reading the -intercept, where the curve meets the vertical axis. The lowest point may look important, but it answers a different question. Match the input first, then read the output.
Hints
- Hint 1
In , is the input: it tells you where to look along the horizontal -axis. For , which vertical axis contains every point with that input?
- Hint 2
A point on the graph says : input gives output . At the matching input, read the curve's vertical coordinate, not its lowest point.
Step-by-step
Read the output from the graph
Step 1Find the input on the graph
No Desmos needed. The given graph shows the point you need. asks for the output when . Points with lie on the vertical -axis, so look where the curve crosses that axis. This crossing is the -intercept.
- Step 2
Read the output at that input
The curve crosses the -axis at . In a graph point , the vertical coordinate is the output, so . The lowest point has a different input, , and doesn't answer this question. Choice B.