Q. Evaluate ∫23x−44x2−15x−3dx. Write your answer in simplest form with all logs condensed into a single logarithm (if necessary).
Perform Polynomial Long Division: We will first perform polynomial long division to simplify the integrand (4x2−15x−3)/(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 4x2−15x−3−(4x2−16x)=x+3. So, the quotient is 4x+1 and the remainder is x+3. The integral can now be rewritten as the integral of 4x+1 plus the integral of the remainder over 4x21.
Integrate Simplified Expression Term by Term: Now we will integrate the simplified expression term by term. The integral of 4x is 2x2, and the integral of 1 is x. For the remainder, we have the integral of (x+3)/(x−4). We can split this into two separate integrals: the integral of x/(x−4) and the integral of 3/(x−4).
Evaluate Antiderivative from 2 to 3: The integral of x/(x−4) can be simplified by recognizing that the derivative of the denominator (x−4) is 1, which matches the numerator x after adjusting for the constant shift. Therefore, the integral of x/(x−4) is ln∣x−4∣. The integral of 3/(x−4) is 3 times the integral of 30, which is 31.
Combine Logarithmic Terms: Combining all the terms, the integral becomes 2x2+x+ln∣x−4∣+3ln∣x−4∣. Since we want to condense the logarithms into a single logarithm, we use the property that ln(a)+ln(b)=ln(ab) to combine the logarithmic terms. This gives us 2x2+x+ln∣(x−4)4∣.
Simplify Integral at Upper and Lower Limits: Now we need to evaluate the antiderivative from 2 to 3. We plug in the upper limit of 3 into the antiderivative to get 2(3)2+3+ln∣(3−4)4∣, which simplifies to 18+3+ln∣(−1)4∣=21+ln∣1∣. Then we plug in the lower limit of 2 into the antiderivative to get 2(2)2+2+ln∣(2−4)4∣, which simplifies to 8+2+ln∣(−2)4∣=10+ln∣16∣.
Subtract Values at Upper and Lower Limits: Subtracting the value at the lower limit from the value at the upper limit, we get (21+ln∣1∣)−(10+ln∣16∣). Since ln∣1∣ is 0, this simplifies to 21−10−ln∣16∣=11−ln∣16∣.
Final Answer: The final answer in simplest form is 11−ln∣16∣.
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