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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 both sides by (x-2)(x+1):4x - 5 = A(x+1) + B(x-2)To find A, set x = 2:4(2) - 5 = A(2+1) + B(0)8 - 5 = 3A3 = 3A => A = 1To find B, set x = -1:4(-1) - 5 = A(0) + B(-1-2)-4 - 5 = -3B-9 = -3B => B = 3So, the integral becomes:∫ [1/(x-2) + 3/(x+1)] dxIntegrate each term:∫ 1/(x-2) dx = ln|x-2| + C1∫ 3/(x+1) dx = 3ln|x+1| + C2Combining them, we get:ln|x-2| + 3ln|x+1| + CThis matches option B (rearranged).

Hint

Begin by factoring the denominator and using partial fraction decomposition.

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