For a quadratic function, the vertex is the graph’s turning point. A positive coefficient makes it the lowest point, so graph the function in Desmos and click that point. The question asks for the vertical, or -, coordinate. Don’t report its distance below the -axis as a positive number.
Hints
- Hint 1
The vertex is where a parabola turns. A positive coefficient of makes the graph open upward, so its vertex is the lowest point. Which point should you click?
- Hint 2
A point is written : the first number gives its horizontal position, and the second number gives its vertical position. After clicking the vertex, which number answers the question?
Step-by-step
Graph and click the vertex
Step 1Identify the point you need
The vertex is the turning point. In , the coefficient of is , which is positive, so the parabola opens upward. Its vertex is the lowest point, not a point where the graph crosses an axis.
- Step 2
Read the vertex’s vertical coordinate
Type in Desmos. Click the curve, then click its lowest marked point. Desmos shows : is the horizontal position, and is the vertical position. For the vertex’s -coordinate, read the second coordinate. So the requested coordinate is . Choice B.