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"If " f(x)=int(dx)/(x^(1//3)+2) " and "f...

`"If " f(x)=int(dx)/(x^(1//3)+2) " and "f(0)=12log_(e)2, " then the value of " f(-1) " is"-.`

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To solve the problem, we need to find the value of \( f(-1) \) given that \[ f(x) = \int \frac{dx}{x^{1/3} + 2} \] and \( f(0) = 12 \ln 2 \). ### Step 1: Change of Variable Let's start by making a substitution to simplify the integral. Let \[ t^3 = x \implies dx = 3t^2 dt. \] ### Step 2: Rewrite the Integral Substituting \( x \) in the integral, we have: \[ f(x) = \int \frac{3t^2 dt}{t + 2}. \] ### Step 3: Simplify the Integral Now, we can separate the integral: \[ f(x) = 3 \int \frac{t^2}{t + 2} dt. \] To simplify \( \frac{t^2}{t + 2} \), we can perform polynomial long division: \[ \frac{t^2}{t + 2} = t - 2 + \frac{4}{t + 2}. \] ### Step 4: Integrate Each Term Now we can integrate: \[ f(x) = 3 \left( \int (t - 2) dt + \int \frac{4}{t + 2} dt \right). \] Calculating each integral: 1. \( \int (t - 2) dt = \frac{t^2}{2} - 2t \) 2. \( \int \frac{4}{t + 2} dt = 4 \ln |t + 2| \) Thus, \[ f(x) = 3 \left( \frac{t^2}{2} - 2t + 4 \ln |t + 2| \right) + C. \] ### Step 5: Substitute Back for \( t \) Substituting back \( t = x^{1/3} \): \[ f(x) = 3 \left( \frac{x^{2/3}}{2} - 2x^{1/3} + 4 \ln |x^{1/3} + 2| \right) + C. \] ### Step 6: Use the Given Condition We know \( f(0) = 12 \ln 2 \). Let's find \( f(0) \): \[ f(0) = 3 \left( 0 - 0 + 4 \ln |2| \right) + C = 12 \ln 2. \] This implies: \[ 12 \ln 2 + C = 12 \ln 2 \implies C = 0. \] ### Step 7: Final Expression for \( f(x) \) Thus, we have: \[ f(x) = \frac{3}{2} x^{2/3} - 6 x^{1/3} + 12 \ln |x^{1/3} + 2|. \] ### Step 8: Calculate \( f(-1) \) Now, we need to find \( f(-1) \): \[ f(-1) = \frac{3}{2} (-1)^{2/3} - 6 (-1)^{1/3} + 12 \ln |-1^{1/3} + 2|. \] Calculating each term: 1. \( (-1)^{2/3} = 1 \) 2. \( (-1)^{1/3} = -1 \) 3. \( |-1^{1/3} + 2| = | -1 + 2 | = 1 \) So, \[ f(-1) = \frac{3}{2} \cdot 1 - 6 \cdot (-1) + 12 \ln 1. \] Since \( \ln 1 = 0 \): \[ f(-1) = \frac{3}{2} + 6 = \frac{3}{2} + \frac{12}{2} = \frac{15}{2}. \] ### Final Answer Thus, the value of \( f(-1) \) is \[ \boxed{\frac{15}{2}}. \]

To solve the problem, we need to find the value of \( f(-1) \) given that \[ f(x) = \int \frac{dx}{x^{1/3} + 2} \] and \( f(0) = 12 \ln 2 \). ...
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