Answer:

Step-by-step explanation:
Vertex form of a quadratic equation;

Vertex of the parabolas (h, k)
The vertex of the parabola is either the minimum or maximum of the parabola. The axis of symmetry goes through the x-coordinate of the vertex, hence h = -3. The minimum of the parabola is the y-coordinate of the vertex, so k= 7. Now substitute it into the formula;

Now substitute in the given point; ( -1, 9) and solve for a;

Hence the equation in vertex form is;

In standard form it is;

The answer is 15.
17^2-8^2=225
sr of 225= 15
:))
The equation of the tangent line can be found using slope formula and fact that slope = dy/dx.

where (x0,y0) is point A ---> (0,-1)
Then rearrange equation into slope-intercept form:

Finally sub in x=0 into dy/dx to get slope at the point (0,-1)
This is the answers from MathPapa