A quadratic written as is in vertex form, which shows where its graph turns. Set the expression inside the square to to find the vertex’s -coordinate, then read the number outside the square for its -coordinate. Watch the inside sign: the vertex’s input makes that expression zero.
Hints
- Hint 1
The vertex is where the graph turns. In vertex form, the squared part is at that point. What value of makes equal ?
- Hint 2
Once the square is , it contributes nothing to the output. The number outside the square gives the vertex’s -coordinate. What number remains?
Step-by-step
Read the vertex from vertex form
Step 1Find where the square is zero
No Desmos needed. The function is already in vertex form. The vertex is the graph’s turning point. In vertex form, the vertex occurs where the squared part is . Set the inside of the square to :
- Step 2
Solve for the vertex’s input
Add to both sides:
Don’t copy the minus sign from : the input must make that expression equal .
- Step 3
Read the vertex’s output
At , the square is , so the outside makes the vertex’s -coordinate . The vertex is . Choice D.