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MTH 102 MTH 102 Past Questions Objective Question

Question

Simplify ∫ (4x-5) / (x2 - x - 2) dx
Options
A ln|x-1| + ln|x+2| + C
B 3ln|x+1| + ln|x-2| + C
Correct Answer
C ln|x-1| - 2ln|x-2| + C
D 4ln|(x-2)/(x-1)| + C
Correct Answer

Option B is the correct answer.

Detailed Explanation

First, factor the denominator: x2 - x - 2 = (x-2)(x+1).Next, use partial fraction decomposition: (4x-5) / ((x-2)(x+1)) = A/(x-2) + B/(x+1).Multiply by (x-2)(x+1) to get: 4x-5 = A(x+1) + B(x-2).Set x = 2: 4(2)-5 = A(2+1) => 3 = 3A => A = 1.Set x = -1: 4(-1)-5 = B(-1-2) => -9 = -3B => B = 3.So the integral becomes ∫ [1/(x-2) + 3/(x+1)] dx.Integrate each term: ∫ 1/(x-2) dx = ln|x-2| and ∫ 3/(x+1) dx = 3ln|x+1|.Combining these gives: ln|x-2| + 3ln|x+1| + C.

Hint

Start by factoring the denominator and using partial fraction decomposition.

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