Q. Evaluate ∫13x−44x2−19x+9dx. Write your answer in simplest form with all logs condensed into a single logarithm (if necessary).
Perform Polynomial Long Division: First, we will perform polynomial long division to simplify the integrand (4x2−19x+9)/(x−4). Dividing 4x2 by x gives us 4x. Multiplying 4x by (x−4) gives us 4x2−16x. Subtracting this from the original numerator, we get −19x+9−(4x2−16x)=−3x+9. Dividing −3x by x gives us 4x20. Multiplying 4x20 by (x−4) gives us 4x23. Subtracting this from the previous remainder, we get 4x24. Since 4x25 is of lower degree than the divisor 4x26, we stop here. The result of the division is 4x27 with a remainder of 4x25. So, the integrand can be rewritten as 4x29.
Split Integral into Two Parts: Now, we can split the integral into two parts: ∫13(4x−3)dx and ∫13x−43x−3dx. The first integral is straightforward to evaluate: ∫(4x−3)dx=2x2−3x+C. Evaluating from 1 to 3 gives us (2(3)2−3(3))−(2(1)2−3(1))=(18−9)−(2−3)=9+1=10.
Evaluate First Integral: The second integral ∫(3x−3)/(x−4)dx from 1 to 3 is more complex. We can rewrite the numerator to match the derivative of the denominator:Let's rewrite 3x−3 as 3(x−4)+12, so the integral becomes ∫(3(x−4)+12)/(x−4)dx.This can be split into two integrals: 3∫(x−4)/(x−4)dx+12∫1/(x−4)dx.The first part simplifies to 3∫1dx, which is just 3x.The second part is 12∫1/(x−4)dx, which is 10.
Rewrite Numerator for Second Integral: Now we can evaluate the second integral from 1 to 3: ∫13dx from 1 to 3 is simply 3x evaluated from 1 to 3, which gives us 3(3)−3(1)=9−3=6. ∫13x−412dx from 1 to 3 is 32 evaluated from 1 to 3, which gives us 35. Since 36 is 37, this simplifies to 38.
Evaluate Second Integral: Combining the results from the two parts of the integral, we have:The integral from 1 to 3 of (4x2−19x+9)/(x−4)dx is equal to 10 (from the first part) plus 6 (from the second part, the 3x term) minus 12ln(3) (from the second part, the logarithmic term).So, the final answer is 16−12ln(3).
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