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Find the average value of the function 
f(x)=(6)/(3-4x) from 
x=1 to 
x=7. Express your answer as a constant times 
ln 5.
Answer: 
◻ln 5

Find the average value of the function f(x)=634x f(x)=\frac{6}{3-4 x} from x=1 x=1 to x=7 x=7 . Express your answer as a constant times ln5 \ln 5 .\newlineAnswer: ln5 \square\ln 5

Full solution

Q. Find the average value of the function f(x)=634x f(x)=\frac{6}{3-4 x} from x=1 x=1 to x=7 x=7 . Express your answer as a constant times ln5 \ln 5 .\newlineAnswer: ln5 \square\ln 5
  1. Understand the concept: Understand the concept of average value of a function.\newlineThe average value of a function f(x)f(x) on the interval [a,b][a, b] is given by the formula:\newlineAverage value = 1(ba)abf(x)dx\frac{1}{(b-a)} \int_{a}^{b} f(x) \, dx\newlineHere, a=1a = 1 and b=7b = 7.
  2. Set up the integral: Set up the integral for the average value.\newlineAverage value = (1/(71))×17634xdx(1/(7-1)) \times \int_{1}^{7} \frac{6}{3-4x} dx\newlineSimplify the coefficient: (1/(71))=1/6(1/(7-1)) = 1/6\newlineSo, Average value = (1/6)×17634xdx(1/6) \times \int_{1}^{7} \frac{6}{3-4x} dx
  3. Simplify the coefficient: Simplify the integral.\newlineThe integral becomes (16)×17634xdx=(16)×6×17134xdx(\frac{1}{6}) \times \int_{1}^{7} \frac{6}{3-4x} dx = (\frac{1}{6}) \times 6 \times \int_{1}^{7} \frac{1}{3-4x} dx\newlineThe 66's cancel out, leaving us with 17134xdx\int_{1}^{7} \frac{1}{3-4x} dx
  4. Simplify the integral: Perform a substitution to solve the integral.\newlineLet u=34xu = 3 - 4x, then du=4dxdu = -4 dx, or dx=14dudx = -\frac{1}{4} du.\newlineWhen x=1x = 1, u=34(1)=1u = 3 - 4(1) = -1.\newlineWhen x=7x = 7, u=34(7)=25u = 3 - 4(7) = -25.\newlineNow, the integral is 125(14)(1u)du\int_{-1}^{-25} (-\frac{1}{4}) \cdot (\frac{1}{u}) du.
  5. Perform a substitution: Evaluate the integral with the new limits of integration.\newlineThe integral becomes (14)125(1u)du=(14)[lnu](-\frac{1}{4}) \cdot \int_{-1}^{-25} (\frac{1}{u}) \, du = (-\frac{1}{4}) \cdot [\ln|u|] from 1-1 to 25-25.
  6. Evaluate the integral: Calculate the value of the integral.\newlinePlugging in the limits, we get (14)×(ln25ln1)=(14)×(ln(25)ln(1))(-\frac{1}{4}) \times (\ln|-25| - \ln|-1|) = (-\frac{1}{4}) \times (\ln(25) - \ln(1)).\newlineSince ln(1)=0\ln(1) = 0, this simplifies to (14)×ln(25)(-\frac{1}{4}) \times \ln(25).
  7. Calculate the value: Simplify the expression. ln(25)\ln(25) can be written as 2×ln(5)2 \times \ln(5), so the expression becomes (14)×2×ln(5)=(12)×ln(5)(-\frac{1}{4}) \times 2 \times \ln(5) = (-\frac{1}{2}) \times \ln(5).
  8. Simplify the expression: Multiply by the coefficient from the average value formula.\newlineThe average value is (16)(\frac{1}{6}) times the integral, so we multiply (12)ln(5)(-\frac{1}{2}) \cdot \ln(5) by 16\frac{1}{6}.\newlineAverage value = (16)(12)ln(5)=(112)ln(5)(\frac{1}{6}) \cdot (-\frac{1}{2}) \cdot \ln(5) = (-\frac{1}{12}) \cdot \ln(5).
  9. Multiply by the coefficient: Check for any mathematical errors.\newlineReviewing the steps, there are no apparent mathematical errors.