Question
For the function \( P(x)=x^{3}-9 x \), at the point \( (3,0) \), find the following. (a) the slope of the tangent to the curve (b) the instantaneous rate of change of the function (b)
Ask by Wang Rodriquez. in the United States
Mar 08,2025
Upstudy AI Solution
Tutor-Verified Answer
Answer
The slope of the tangent at \( (3,0) \) is 18, and the instantaneous rate of change of the function at \( x = 3 \) is also 18.
Solution
To find the slope of the tangent to the curve at the point \( (3,0) \) for the function \( P(x) = x^{3} - 9x \), we need to find the derivative of the function and then evaluate it at \( x = 3 \).
The derivative of \( P(x) \) with respect to \( x \) is given by:
\[ P'(x) = \frac{d}{dx}(x^{3} - 9x) \]
Using the power rule for differentiation, we have:
\[ P'(x) = 3x^{2} - 9 \]
Now, we need to find the instantaneous rate of change of the function at \( x = 3 \), which is the value of \( P'(3) \).
Substitute \( x = 3 \) into the derivative \( P'(x) \):
\[ P'(3) = 3(3)^{2} - 9 \]
Calculate the value of \( P'(3) \) to find the instantaneous rate of change of the function at \( x = 3 \).
Calculate the value by following steps:
- step0: Calculate:
\(3\times 3^{2}-9\)
- step1: Calculate:
\(3^{3}-9\)
- step2: Evaluate the power:
\(27-9\)
- step3: Subtract the numbers:
\(18\)
The slope of the tangent to the curve at the point \( (3,0) \) for the function \( P(x) = x^{3} - 9x \) is 18.
The instantaneous rate of change of the function at \( x = 3 \) is also 18.
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Extra Insights
To find the slope of the tangent to the curve at the point \( (3,0) \) for the function \( P(x) = x^{3} - 9x \), we first need to compute the derivative of the function. The derivative \( P'(x) \) can be calculated using the power rule: \[ P'(x) = 3x^{2} - 9 \] Next, we evaluate the derivative at \( x = 3 \): \[ P'(3) = 3(3)^{2} - 9 = 3(9) - 9 = 27 - 9 = 18 \] So, the slope of the tangent line at the point \( (3, 0) \) is \( 18 \). Therefore, the instantaneous rate of change of the function at \( x = 3 \) is also \( 18 \).