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MTH 102 MTH 102 Past Questions Objective Question

Question

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

Option D is the correct answer.

Detailed Explanation

Differentiate each term separately. Assume "log" refers to the natural logarithm (ln), as is common in calculus when no base is specified. If it were base 10, it would be log10. The derivative of logb(u) is (1/(u ln b)) du/dx. For ln(u), it is (1/u) du/dx. For d/dx(au) = au ln(a) du/dx.1. d/dx [log(x3 - x)]: Using the chain rule, this is (1/(x3 - x)) * d/dx(x3 - x) = (1/(x(x2 - 1))) * (3x2 - 1) = (3x2 - 1) / (x(x2 - 1))2. d/dx [7(2/3)x]: Using the formula d/dx(au) = au ln(a) du/dx. Here a=7, u=(2/3)x, so du/dx = 2/3. = 7(2/3)x * ln(7) * (2/3)Combine the derivatives:dy/dx = (3x2 - 1) / (x(x2 - 1)) + 7(2/3)x (2/3) ln(7).Since ln(7) can be written as log 7 (if 'log' refers to natural logarithm in the context of the options), this matches option D.

Hint

Differentiate the logarithmic term using the chain rule and the exponential term using the rule for d/dx(au).

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