Q. Find the average value of the function f(x)=3−4x6 from x=1 to x=7. Express your answer as a constant times ln5.Answer: □ln5
Understand the concept: Understand the concept of average value of a function.The average value of a function f(x) on the interval [a,b] is given by the formula:Average value = (b−a)1∫abf(x)dxHere, a=1 and b=7.
Set up the integral: Set up the integral for the average value.Average value = (1/(7−1))×∫173−4x6dxSimplify the coefficient: (1/(7−1))=1/6So, Average value = (1/6)×∫173−4x6dx
Simplify the coefficient: Simplify the integral.The integral becomes (61)×∫173−4x6dx=(61)×6×∫173−4x1dxThe 6's cancel out, leaving us with ∫173−4x1dx
Simplify the integral: Perform a substitution to solve the integral.Let u=3−4x, then du=−4dx, or dx=−41du.When x=1, u=3−4(1)=−1.When x=7, u=3−4(7)=−25.Now, the integral is ∫−1−25(−41)⋅(u1)du.
Perform a substitution: Evaluate the integral with the new limits of integration.The integral becomes (−41)⋅∫−1−25(u1)du=(−41)⋅[ln∣u∣] from −1 to −25.
Evaluate the integral: Calculate the value of the integral.Plugging in the limits, we get (−41)×(ln∣−25∣−ln∣−1∣)=(−41)×(ln(25)−ln(1)).Since ln(1)=0, this simplifies to (−41)×ln(25).
Calculate the value: Simplify the expression. ln(25) can be written as 2×ln(5), so the expression becomes (−41)×2×ln(5)=(−21)×ln(5).
Simplify the expression: Multiply by the coefficient from the average value formula.The average value is (61) times the integral, so we multiply (−21)⋅ln(5) by 61.Average value = (61)⋅(−21)⋅ln(5)=(−121)⋅ln(5).
Multiply by the coefficient: Check for any mathematical errors.Reviewing the steps, there are no apparent mathematical errors.