A quadratic graph that opens downward has a vertex, its highest point. To find the maximum value of the function, read the height of that point: its -coordinate. If the graph is already shown, you don't need to redraw it in Desmos. Be careful not to choose a nearby point's height instead.
Hints
- Hint 1
The vertex is where the parabola turns. Because this curve opens downward, its vertex is the highest point. Can you find that point on the graph?
- Hint 2
A point on pairs an input with an output: the -coordinate is the input, and the -coordinate is the output. The maximum value is an output, so which coordinate of the highest point do you need?
Step-by-step
Read the highest point
Step 1Locate the maximum point
No Desmos needed. The graph already shows the peak. The parabola opens downward, so its vertex, the point where it turns, is its highest point.
- Step 2
Read the maximum value
The vertex is . Its first coordinate, , tells you where the maximum happens; its second coordinate, , is the height. A function's maximum value is the -coordinate of its highest point. So the maximum value of is . Choice B.