Q. For the following equation, what is the instantaneous rate of change at x=−2?f(x)=−x3−2xAnswer:
Calculate Derivative: To find the instantaneous rate of change of the function at a specific point, we need to calculate the derivative of the function. The derivative of a function at a point gives us the slope of the tangent line at that point, which is the instantaneous rate of change.
Apply Power Rule: The function given is f(x)=−x3−2x. We will find the derivative f′(x) using the power rule. The power rule states that the derivative of xn is n⋅x(n−1).
Evaluate at x=−2: Applying the power rule to each term in the function:The derivative of −x3 is −3x2 (using the power rule).The derivative of −2x is −2 (since the derivative of x is 1 and the constant multiple rule applies).So, f′(x)=−3x2−2.
Substitute and Calculate: Now we need to evaluate the derivative at x=−2 to find the instantaneous rate of change at that point.Substitute x=−2 into f′(x):f′(−2)=−3(−2)2−2.
Substitute and Calculate: Now we need to evaluate the derivative at x=−2 to find the instantaneous rate of change at that point.Substitute x=−2 into f′(x):f′(−2)=−3(−2)2−2.Calculate the value:f′(−2)=−3(4)−2=−12−2=−14.
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