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Find the value of 
int_(1)^(4)(4)/(2x-9)dx. Express your answer as a constant times 
ln 7.
Answer: 
◻ln 7

Find the value of 1442x9dx \int_{1}^{4} \frac{4}{2 x-9} d x . Express your answer as a constant times ln7 \ln 7 .\newlineAnswer: ln7 \square \ln 7

Full solution

Q. Find the value of 1442x9dx \int_{1}^{4} \frac{4}{2 x-9} d x . Express your answer as a constant times ln7 \ln 7 .\newlineAnswer: ln7 \square \ln 7
  1. Recognize standard form: Recognize the integral as a standard form. The integral 42x9dx\int \frac{4}{2x-9}\,dx can be recognized as a standard form of the integral of a function of the form 1u\frac{1}{u}, which is lnu+C\ln|u| + C, where CC is the constant of integration.
  2. Perform substitution to simplify: Perform a substitution to simplify the integral.\newlineLet u=2x9u = 2x - 9, then dudx=2\frac{du}{dx} = 2, or dx=du2dx = \frac{du}{2}. The integral becomes 4u(du2)\int \frac{4}{u} \cdot \left(\frac{du}{2}\right).
  3. Simplify the integral: Simplify the integral.\newlineThe integral simplifies to 2(1u)du2\int(\frac{1}{u})\,du, which is 2lnu+C2\ln|u| + C.
  4. Substitute back for uu: Substitute back for uu. Substitute back u=2x9u = 2x - 9 into the integral to get 2ln2x9+C2\ln|2x - 9| + C.
  5. Evaluate definite integral: Evaluate the definite integral from 11 to 44. We need to evaluate 2ln2x92\ln|2x - 9| from x=1x = 1 to x=4x = 4. This gives us 2ln2(4)92ln2(1)92\ln|2(4) - 9| - 2\ln|2(1) - 9|, which simplifies to 2ln892ln292\ln|8 - 9| - 2\ln|2 - 9|.
  6. Simplify expression: Simplify the expression.\newlineSince ln89=ln1=0\ln|8 - 9| = \ln|1| = 0 and ln29=ln7=ln7\ln|2 - 9| = \ln|-7| = \ln|7| (because the natural logarithm function is even), the expression simplifies to 02ln70 - 2\ln|7|.
  7. Final answer: Simplify the final answer.\newlineThe final answer is 2ln7-2\ln|7|, which can be expressed as 2ln7-2\ln7 because 77 is positive and we do not need the absolute value.