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Question
Math
Posted 11 months ago
7. If f(x)=1x311+lntdtf(x)=\int_{1}^{x^{3}} \frac{1}{1+\ln t} d t for x1x \geq 1, then f(2)=f^{\prime}(2)=
(A) 11+ln2\frac{1}{1+\ln 2}
(B) 121+ln2\frac{12}{1+\ln 2}
(C) 11+ln8\frac{1}{1+\ln 8}
(D) 121+ln8\frac{12}{1+\ln 8}
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Answer from Sia
Posted 11 months ago
Solution by Steps
step 2
Applying this to f(x)=1x311+lntdt f(x) = \int_{1}^{x^3} \frac{1}{1+\ln t} dt , we get f(x)=11+ln(x3)ddx(x3) f'(x) = \frac{1}{1+\ln(x^3)} \cdot \frac{d}{dx}(x^3) ..
step 3
The derivative of x3 x^3 is 3x2 3x^2 , so f(x)=3x21+ln(x3) f'(x) = \frac{3x^2}{1+\ln(x^3)} ..
step 4
To find f(2) f'(2) , we substitute x=2 x = 2 into the derivative to get f(2)=3(2)21+ln(23) f'(2) = \frac{3(2)^2}{1+\ln(2^3)} ..
step 5
Simplifying, we find f(2)=121+ln8 f'(2) = \frac{12}{1+\ln 8} ..
D
Key Concept
Fundamental Theorem of Calculus Part 1
Explanation
The derivative of the integral from a constant to a function of x x is the integrand evaluated at the function times the derivative of the function.

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