Question Detail

MTH 102 MTH 102 Past Questions Objective Question

Question

Evaluate ∫₁⁴ (1/8 x^(3/2) - 4/x) dx, for x > 0.
Options
A 2
B 3
C 4
Correct Answer
D 5
Correct Answer

Option C is the correct answer.

Detailed Explanation

First, find the indefinite integral of each term:∫ (1/8 x^(3/2)) dx = (1/8) * (x^(3/2 + 1)) / (3/2 + 1) = (1/8) * (x^(5/2)) / (5/2) = (1/8) * (2/5) * x^(5/2) = (1/20) x^(5/2).∫ (-4/x) dx = -4 ln|x|.So the indefinite integral is (1/20) x^(5/2) - 4 ln|x|.Now, evaluate the definite integral from 1 to 4:[(1/20) x^(5/2) - 4 ln|x|]₁⁴= [(1/20) 4^(5/2) - 4 ln 4] - [(1/20) 1^(5/2) - 4 ln 1]= [(1/20) * (√4)⁵ - 4 ln 4] - [(1/20) * 1 - 4 * 0]= [(1/20) * 2⁵ - 4 ln 4] - [1/20]= [32/20 - 4 ln 4] - [1/20]= 31/20 - 4 ln 4.Numerically, 31/20 ≈ 1.55 and 4 ln 4 ≈ 4 * 1.386 = 5.544. So, 1.55 - 5.544 = -3.994.It appears there might be a sign error in the original question or the options, as the calculation leads to approximately -4. If the integrand was (4/x - 1/8 x^(3/2)), the result would be approximately 4. Assuming the intended answer is 4, as indicated by the options and markings.

Hint

Integrate each term using the power rule for integration (∫xⁿ dx = xⁿ⁺¹/(n+1)) and the integral of 1/x (∫1/x dx = ln|x|). Then evaluate at the limits.

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