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18 votes
18 votes
The question is in the image

The question is in the image-example-1
User LongZheng
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1 Answer

18 votes
18 votes

Answer:

h(t) = -5*t^2 + 20*t + 2

Explanation:

First, we know that the motion equation of the ball will be quadratic, so we write the equation:

h(t) = a*t^2 + b*t + c

Now we need to work with the data in the table.

h(1) = 17

h(3) = 17

h(1) = h(2) = 17

Then we have a symmetry around:

(3 - 1)/2 + 1 = 2

Remember that the symmetry is around the vertex of the parabola, then we can conclude that the vertex of the parabola is the point:

(2, h(2)) = (2, 22)

Remember that for a quadratic equation:

y = a*x^2 + b*x + c

with a vertex (h, k)

we can rewrite our function as:

y = a*(x - h)^2 + k

So in this case, we can rewrite our function as:

h(t) = a*(t - 2)^2 + 22

To find the value of a, notice the first point in the table:

(0, 2)

then we have:

h(0) = 2 = a*(0 - 2)^2 + 22

= 2 = a*(-2)^2 + 22

2 = a*(4) + 22

2 - 22 = a*(4)

-20/4 = -5 = a

Then our function is:

h(t) = -5*(t - 2)^2 + 22

Now we just expand it:

h(t) = -5*(t^2 - 4*t + 4) + 22

h(t) = -5*t^2 + 20*t + 2

The correct option is the first one.

User Nsanglar
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