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Let f:R rarr R be a function as f(x)=(...

Let `f:R rarr R` be a function as
`f(x)=(x-1)(x+2)(x-3)(x-6)-100`. If `g(x)` is a polynomial of degree `le 3` such that `int (g(x))/(f(x))dx` does not contain any logarithm function and `g(-2)=10`. Then
`int (g(x))/(f(x))dx`, equals

A

`tan^(-1)((x-2)/(2))+c`

B

`tan^(-1)((x-1)/(1))+c`

C

`tan^(-1)(x)+c`

D

None of these

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem step by step, we need to find the integral of \( \frac{g(x)}{f(x)} \, dx \) where \( f(x) = (x-1)(x+2)(x-3)(x-6) - 100 \) and \( g(-2) = 10 \). We also need to ensure that the integral does not contain any logarithmic functions. ### Step 1: Expand \( f(x) \) First, we need to expand the function \( f(x) \). \[ f(x) = (x-1)(x+2)(x-3)(x-6) - 100 \] Calculating \( (x-1)(x+2) \): \[ (x-1)(x+2) = x^2 + x - 2 \] Calculating \( (x-3)(x-6) \): \[ (x-3)(x-6) = x^2 - 9x + 18 \] Now, we multiply these two results: \[ f(x) = (x^2 + x - 2)(x^2 - 9x + 18) - 100 \] Expanding this product: \[ = x^4 - 9x^3 + 18x^2 + x^3 - 9x^2 - 18 - 2x^2 + 18x - 36 - 100 \] Combining like terms: \[ = x^4 - 8x^3 + 7x^2 + 18x - 154 \] ### Step 2: Set up the integral We need to find \( \int \frac{g(x)}{f(x)} \, dx \) where \( g(x) \) is a polynomial of degree \( \leq 3 \). ### Step 3: Use Partial Fraction Decomposition Since \( f(x) \) is a polynomial of degree 4, we can express \( \frac{g(x)}{f(x)} \) using partial fractions. We assume: \[ \frac{g(x)}{f(x)} = \frac{A}{x^2 - 4x + 8} + \frac{B}{x^2 - 4x - 17} \] where \( A \) and \( B \) are polynomials of degree less than or equal to 1. ### Step 4: Determine conditions for \( g(x) \) For the integral to not contain logarithmic functions, we need the linear terms in the numerators of the partial fractions to vanish. Thus, we set: \[ A = 0 \quad \text{and} \quad C = 0 \] This means \( g(x) \) must be a constant polynomial. ### Step 5: Find \( g(x) \) Since \( g(-2) = 10 \), we can conclude: \[ g(x) = 10 \] ### Step 6: Evaluate the integral Now we evaluate: \[ \int \frac{10}{f(x)} \, dx \] ### Step 7: Final result The integral simplifies to: \[ \int \frac{10}{(x-1)(x+2)(x-3)(x-6) - 100} \, dx \] This integral can be evaluated using appropriate techniques, but we have established that \( g(x) = 10 \) and \( f(x) \) is as defined above. ### Conclusion Thus, the final answer for the integral \( \int \frac{g(x)}{f(x)} \, dx \) is: \[ \int \frac{10}{f(x)} \, dx \]
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