Step-by-step explanation:
You want the to find the value of k such that the y coordinate of the vertex is 0.
0=x2−6x+k
The x coordinate, h, of the vertex is found, using the following equation:
h=−b2a
h=−−62(1)=3
Evaluate at x = 3:
0=32−6(3)+k
k=9
