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MTH 102 MTH 102 Past Questions Objective Question

Question

Obtain d⁄dx {ln(x2 ⁄ (x2+1))}
Options
A 2 ⁄ (x(x<sup>2</sup>+1))
Correct Answer
B -2 ⁄ (x(x<sup>2</sup>+1))
C -5 ⁄ (x(x<sup>2</sup>+1))
D 5 ⁄ (x(x<sup>2</sup>+1))
Correct Answer

Option A is the correct answer.

Detailed Explanation

First, simplify the logarithmic expression using the property ln(a⁄b) = ln a - ln b, which gives ln(x2) - ln(x2+1). This can be further written as 2ln|x| - ln(x2+1). Now, differentiate each term. The derivative of 2ln|x| is 2/x. The derivative of ln(x2+1) using the chain rule is (1⁄(x2+1)) * (2x) = 2x⁄(x2+1). Subtracting these gives 2/x - 2x⁄(x2+1). Combining them with a common denominator, x(x2+1), results in (2(x2+1) - 2x2) ⁄ (x(x2+1)) = (2x2 + 2 - 2x2) ⁄ (x(x2+1)) = 2 ⁄ (x(x2+1)).

Hint

Simplify the logarithm before differentiating. Remember the chain rule for ln(f(x)).

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