Q. The derivative of the function f is defined by f′(x)=x3−5+2sin(2x−5). Find the x values, if any, in the interval −0.5<x<2.5 where the function f has a relative maximum. You may use a calculator and round all values to 3 decimal places.Answer: x=
Find Critical Points: To find the relative maximum of the function f, we need to find the critical points of f′(x) in the given interval. Critical points occur where the derivative is zero or undefined. The derivative f′(x)=x3−5+2sin(2x−5) is defined for all x, so we only need to find where it is zero.
Solve for x: Set the derivative equal to zero and solve for x:x3−5+2sin(2x−5)=0This equation is not easily solvable algebraically, so we will use a calculator to find the approximate values of x in the interval -0.5 < x < 2.5.
Graph Function: Using a calculator, we graph the function f′(x)=x3−5+2sin(2x−5) and look for points where the graph crosses the x-axis within the interval -0.5 < x < 2.5.
Check Sign Change: After graphing, we find that the derivative crosses the x-axis at approximately x=1.047. We need to check if this is a relative maximum by looking at the sign of the derivative before and after this point.
Verify Relative Maximum: We test the sign of the derivative around x=1.047. If the derivative changes from positive to negative at x=1.047, then it is a relative maximum.
Verify Relative Maximum: We test the sign of the derivative around x=1.047. If the derivative changes from positive to negative at x=1.047, then it is a relative maximum.Using the calculator, we find that the derivative is positive just before x=1.047 and negative just after x=1.047. Therefore, x=1.047 is a relative maximum.
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