Determine the critical numbers, if any, of the function f on the interval [1,8].f(x)=x28−xGive your answer as a comma-separated list. Express numbers in exact form. If the function does not have any critical numbers, enter DNE.
Q. Determine the critical numbers, if any, of the function f on the interval [1,8].f(x)=x28−xGive your answer as a comma-separated list. Express numbers in exact form. If the function does not have any critical numbers, enter DNE.
Identify Critical Numbers: Identify the critical numbers of the function f(x)=x28−x. Critical numbers occur where the derivative f′(x) is zero or undefined.
Calculate Derivative: Calculate the derivative of f(x)=x28−x. Use the product rule and the chain rule.f′(x)=dxd[x2]8−x+x2dxd[8−x]f′(x)=2x8−x+x2(21)(8−x)−21(−1)f′(x)=2x8−x−(28−xx2)
Simplify Derivative: Simplify the derivative to find where it is zero or undefined.f′(x)=2⋅8−x2x⋅(8−x)−x2f′(x)=2⋅8−x16x−2x2−x2f′(x)=2⋅8−x16x−3x2
Find Zeroes: Set the numerator equal to zero to find where the derivative is zero.16x−3x2=0x(16−3x)=0x=0 or x=316
Check Values: Check if the values found are in the interval [1,8].x=0 is not in the interval [1,8].x=316 is approximately 5.33, which is in the interval [1,8].
Check Undefined Points: Check for points where the derivative is undefined by setting the denominator equal to zero.2⋅8−x=08−x=08−x=0x=8
Verify Endpoint: Verify that x=8 is in the interval [1,8]. Since 8 is the endpoint of the interval, it is considered a critical number if the function is defined there.
Combine Critical Numbers: Combine the results from steps 5 and 7 to list all critical numbers in the interval [1,8].The critical numbers are x=316 and x=8.