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The path of a baseball relative to the ground can be modelled by the function 𝑑(𝑡)=−𝑡2+8𝑡+1 where 𝑑(𝑡) represents the height of the ball in metres after 𝑡 seconds.Find the average rate of change of the ball between 1 and 3 seconds. Bold text start[4 marks]Bold text EndUsing the secant method, find the instantaneous rate of change at 2 seconds.

Question

The path of a baseball relative to the ground can be modelled by the function 𝑑(𝑡)=−𝑡2+8𝑡+1 where 𝑑(𝑡) represents the height of the ball in metres after 𝑡 seconds.Find the average rate of change of the ball between 1 and 3 seconds. Bold text start[4 marks]Bold text EndUsing the secant method, find the instantaneous rate of change at 2 seconds.

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Solution

To find the average rate of change of the ball between 1 and 3 seconds, we need to substitute these values into the function and find the difference in the heights, then divide by the difference in time.

First, find the height at 1 second: d(1) = -(1)^2 + 8(1) + 1 = -1 + 8 + 1 = 8 meters

Then, find the height at 3 seconds: d(3) = -(3)^2 + 8(3) + 1 = -9 + 24 + 1 = 16 meters

The average rate of change between 1 and 3 seconds is then (16 - 8) / (3 - 1) = 8 / 2 = 4 meters per second.

To find the instantaneous rate of change at 2 seconds using the secant method, we need to find the average rate of change over an interval that is very close to 2 seconds. Let's use 1.999 seconds and 2.001 seconds for this.

First, find the height at 1.999 seconds: d(1.999) = -(1.999)^2 + 8(1.999) + 1 = 7.996001 meters

Then, find the height at 2.001 seconds: d(2.001) = -(2.001)^2 + 8(2.001) + 1 = 8.004001 meters

The instantaneous rate of change at 2 seconds is then (8.004001 - 7.996001) / (2.001 - 1.999) = 0.008 / 0.002 = 4 meters per second.

This problem has been solved

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