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;

Answer:
112.5ft^2
Step-by-step explanation:
10 x 9 = 90
9 × 5 × .5 = 22.5
90 + 22.5 = 112.5
2/10 because 0.7/7 is equal to one tenth, so 1.4/7 is equal to 2/10
X = velocity of plane
y = velocity of wind
x - y = 1680/5 = 336 mph .....(1) [ plane flying against the wind]
&
x + y = 1680/4 = 420 mph....(2) [ plane flying with the wind]
Adding (1) and (2) to eliminate y gives
2x = 756
x = 378 mph is the speed of the plane with no wind.