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What is the greatest height the object reached? round the answer to the nearest whole meter.

1 Answer

6 votes

Since we can not determine the exact value with just seeing the graph, it would be necessary to find the equation of the parabola and find the vertex.

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

We can use the point (0, 10) to find c

10= a*(0)^2 + b*(0) + c (Replacing x=0 (t=0) and y=10)

10 = c

Replacing the points (1.5 , 75) and (3.5, 90), we have

75= a*(1.5)^2 + b*(1.5) + 10 (Equation 1)

75= 2.25*a + 1.5*b + 10 (Raising 1.5 to the power of 2) (Equation 1)

65 = 2.25*a + 1.5*b (Subtracting 10 from both sides of the equation)(Equation 1)

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90= a*(3.5)^2 + b*(3.5) + 10 (Equation 2)

90= 12.25*a + 3.5*b + 10 (Raising 3.5 to the power of 2) (Equation 2)

80= 12.25*a + 3.5*b (Subtracting 10 from both sides of the equation)(Equation 2)

We are going to solve the system with the elimination method.

-455 = -15.75*a - 10.5*b (Multiplying equation 1 by -7)

+ 240= 36.75*a + 10.5*b (Multiplying equation 1 by 3)

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-215 = 21*a (Adding equations)

-215/21 = a (Dividing by 21 on both sides of the equation)

-10.238=a (Dividing)

Replacing a=-10.328 in the equation 1, we have:

-455 = -15.75*(-10.328) - 10.5*b

-455 = +162.666 - 10.5*b (Multiplying)

-455 - 162.666 = - 10.5*b (Subtracting 162.666 from both sides of the equation)

-617.334 = -10.5*b

b = 58.825 (Dividing by -10.5 on both sides of the equation)

Using the formula for the vertex of the parabola we have:

Vx= -b/ (2a)

Vx= -58.825/(2*10.5)

Vx= 2.8

Replacing Vx in the parabola we have:

y = (-10.238)*(2.8)^2 + (58.825)*(2.8) + 10

y= 94.44

The answer is 94 rounded to the nearest meter.

User Mcvkr
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