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MTH 102 MTH 102 Past Questions Objective Question

Question

Differentiate y = log (x3 - x) + 7(3⁄2)x
Options
A <sup>3x<sup>2</sup>-1</sup>⁄<sub>x(x<sup>2</sup>-1)</sub> - 7<sup>(3⁄2)x</sup> (<sup>2</sup>⁄<sub>3</sub> log 7)
B -<sup>3x<sup>2</sup>-1</sup>⁄<sub>x(x<sup>2</sup>-1)</sub> - 7<sup>(3⁄2)x</sup> (<sup>2</sup>⁄<sub>3</sub> log 7)
C -<sup>3x<sup>2</sup>-1</sup>⁄<sub>x(x<sup>2</sup>-1)</sub> + 7<sup>-(3⁄2)x</sup> (<sup>2</sup>⁄<sub>3</sub> log 7)
D <sup>3x<sup>2</sup>-1</sup>⁄<sub>x(x<sup>2</sup>-1)</sub> + 7<sup>(3⁄2)x</sup> (<sup>2</sup>⁄<sub>3</sub> log 7)
Correct Answer
Correct Answer

Option D is the correct answer.

Detailed Explanation

First, differentiate y = log(x3 - x). Assuming 'log' refers to the natural logarithm (ln), the derivative is (1⁄(x3-x)) * (3x2-1) using the chain rule. This simplifies to 3x2-1⁄x(x2-1). Next, differentiate 7(3⁄2)x. The derivative of au (where u is a function of x) is au * ln a * du⁄dx. Here, a=7 and u=(3⁄2)x, so du⁄dx = 3⁄2. Thus, the derivative is 7(3⁄2)x * ln 7 * (3⁄2). Combining these, dy⁄dx = 3x2-1⁄x(x2-1) + (3⁄2) * 7(3⁄2)x * ln 7. Option 'D' provides the correct first term. The second term, '7(3⁄2)x (2⁄3 log 7)', appears to have a typo in the coefficient (should be 3⁄2 not 2⁄3) and potentially the base of the logarithm (should be ln 7 if it's natural log, or ln(7)⁄ln(10) if 'log' means base 10). Assuming the intended term matches the calculated derivative, option D is the best fit.

Hint

Remember the chain rule for logarithms and the differentiation rule for exponential functions au.

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