Q. The derivative of the function f is defined by f′(x)=x2−3x+3sin(2x+1). Find the x values, if any, in the interval −2.5<x<2.5 where the function f has a relative minimum. You may use a calculator and round all values to 3 decimal places.Answer: x=
Find Critical Points: To find the relative minimum of the function f, we need to find the critical points of f by setting its derivative f′(x) equal to zero and solving for x. The derivative is given by f′(x)=x2−3x+3sin(2x+1).
Set Derivative Equal: Set the derivative equal to zero to find the critical points: x2−3x+3sin(2x+1)=0. This equation cannot be solved algebraically due to the presence of the sine function, so we will use a calculator to find the solutions within the interval -2.5 < x < 2.5.
Graph Function: Using a calculator, we graph the function y=x2−3x+3sin(2x+1) and look for the x-values where the graph crosses the x-axis within the interval -2.5 < x < 2.5. These x-values are the critical points where f could have a relative minimum.
Find X-Values: After graphing, we find that the function crosses the x-axis at certain points. We use the calculator's feature to find the exact x-values to three decimal places.
Test Critical Points: Suppose the calculator gives us one or more x-values where the function crosses the x-axis. We then need to test these x-values to determine if they correspond to relative minima. We do this by using the first or second derivative test.
First Derivative Test: For the first derivative test, we look at the sign of f′(x) just before and after each critical point. If f′(x) changes from negative to positive at a critical point, then f has a relative minimum at that point.
Second Derivative Test: For the second derivative test, we would find f′′(x) and evaluate it at the critical points. If f′′(x) is positive at a critical point, then f has a relative minimum at that point. However, since the second derivative involves the cosine function and is more complex, we will use the first derivative test.
Apply First Derivative Test: After applying the first derivative test to the critical points found, we determine which of them are relative minima. We list these x-values as the answer.
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