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Find the value of 
int_(6)^(8)(4dx)/(4-x). Express your answer as a constant times 
ln 2.
Answer: 
◻ln 2

Find the value of 684dx4x \int_{6}^{8} \frac{4 d x}{4-x} . Express your answer as a constant times ln2 \ln 2 .\newlineAnswer: ln2 \square \ln 2

Full solution

Q. Find the value of 684dx4x \int_{6}^{8} \frac{4 d x}{4-x} . Express your answer as a constant times ln2 \ln 2 .\newlineAnswer: ln2 \square \ln 2
  1. Recognize standard form: Recognize the integral as a standard form.\newlineThe integral 4dx4x\int \frac{4dx}{4-x} can be recognized as a standard form of the integral ABxdx\int \frac{A}{B-x}dx, which can be solved by using the substitution method.
  2. Use substitution to simplify: Use substitution to simplify the integral.\newlineLet u=4xu = 4-x, then du=dxdu = -dx. We need to adjust the integral to match this substitution, so we multiply by 1-1 inside and outside the integral to get 4duu-\int \frac{-4du}{u}.
  3. Rewrite in terms of u: Rewrite the integral in terms of u.\newlineThe integral now becomes 41udu-4 \int \frac{1}{u} du, which is a standard form for the natural logarithm function.
  4. Integrate with respect to u: Integrate with respect to u.\newlineThe integral of 1u\frac{1}{u} with respect to u is lnu\ln|u|, so the integral becomes 4lnu+C-4 \ln|u| + C, where C is the constant of integration. However, since we are evaluating a definite integral, we do not need to include the constant of integration.
  5. Substitute back in x: Substitute back in terms of x.\newlineWe originally let u=4xu = 4-x, so we substitute back to get 4ln4x-4 \ln|4-x|.
  6. Evaluate definite integral: Evaluate the definite integral from 66 to 88.\newlineWe need to evaluate 4ln4x-4 \ln|4-x| from 66 to 88. This gives us 4[ln48ln46]-4 [\ln|4-8| - \ln|4-6|].
  7. Simplify expression: Simplify the expression.\newlineWe have 4[ln4ln2]-4 [\ln|-4| - \ln|-2|], which simplifies to 4[ln(4)ln(2)]-4 [\ln(4) - \ln(2)].
  8. Combine logarithms: Use properties of logarithms to combine the terms.\newlineWe can use the property ln(a)ln(b)=ln(ab)\ln(a) - \ln(b) = \ln(\frac{a}{b}) to combine the logarithms: 4ln(42)-4 \ln(\frac{4}{2}).
  9. Simplify logarithm: Simplify the logarithm.\newlineSince 42=2\frac{4}{2} = 2, we have 4ln(2)-4 \ln(2).
  10. Express as constant times ln(22): Express the answer as a constant times ln(2)\ln(2).\newlineThe final answer is 4ln(2)-4 \ln(2), which is the value of the definite integral from 66 to 88.