Question Detail

MTH 102 MTH 102 Past Questions Objective Question

Question

Simplify ∫ (4x-5) / (x^2-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). Now, 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. Integrating term by term: ∫ (1/(x-2)) dx = ln|x-2| + C, and ∫ (3/(x+1)) dx = 3ln|x+1| + C. Combining them, we get ln|x-2| + 3ln|x+1| + C.

Hint

Start by factoring the denominator and using partial fraction decomposition.

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