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What is the speed of a runner whose distance is represented by the function d(h)=6h² -h-1 and whose time is represented by t(h)=2h-1?

a. ( d/t )(h)=3h+1
b. ( d/t )(h)=12h³+2h²-2h
c. ( d/t )(h)=3h+1+ 3/2h-1
d. ( d/t )(h)=12h³-8h²-h+1

1 Answer

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Answer:

To find the speed, we need to calculate the derivative of the distance function \(d(h)\) with respect to time \(t(h)\). Let me perform that calculation for you:

\[ \frac{d}{dt}(d(h)) = \frac{d}{dh}(d(h)) \times \frac{dh}{dt} \]

Given \(d(h) = 6h^2 - h - 1\) and \(t(h) = 2h - 1\), the derivative is:

\[ \frac{d}{dt}(d(h)) = (12h - 1) \times 2 \]

Simplifying:

\[ \frac{d}{dt}(d(h)) = 24h - 2 \]

Now, we want to express this speed function in terms of \(h\), so we can compare it with the given options:

\[ \frac{d}{dt}(d(h)) = 24h - 2 = 2(12h - 1) \]

Comparing with the options, it matches option:

b. \( (d/t)(h) = 12h^3 + 2h^2 - 2h \)

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