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Evaluate 
int_(5)^(7)(2x^(2)-17 x+5)/(x-8)dx. Write your answer in simplest form with all logs condensed into a single logarithm (if necessary).

Evaluate 572x217x+5x8dx \int_{5}^{7} \frac{2 x^{2}-17 x+5}{x-8} d x . Write your answer in simplest form with all logs condensed into a single logarithm (if necessary).

Full solution

Q. Evaluate 572x217x+5x8dx \int_{5}^{7} \frac{2 x^{2}-17 x+5}{x-8} d x . Write your answer in simplest form with all logs condensed into a single logarithm (if necessary).
  1. Perform Polynomial Long Division: Perform polynomial long division to simplify the integrand.\newlineWe need to divide the polynomial 2x217x+52x^2 - 17x + 5 by x8x - 8.\newline2x217x+5:(x8)=2x+12x^2 - 17x + 5 : (x - 8) = 2x + 1 with a remainder of 21x321x - 3.\newlineSo, (2x217x+5)/(x8)=2x+1+(21x3)/(x8)(2x^2 - 17x + 5)/(x - 8) = 2x + 1 + (21x - 3)/(x - 8).
  2. Write Integral with Simplified Integrand: Write the integral with the simplified integrand.\newlineNow we can write the integral as:\newline57(2x+1+21x3x8)dx\int_{5}^{7} (2x + 1 + \frac{21x - 3}{x - 8}) \, dx.\newlineThis can be split into three separate integrals:\newline572xdx\int_{5}^{7} 2x \, dx + 571dx\int_{5}^{7} 1 \, dx + 5721x3x8dx\int_{5}^{7} \frac{21x - 3}{x - 8} \, dx.
  3. Integrate Each Term Separately: Integrate each term separately.\newlineThe first integral is 572xdx=x2\int_{5}^{7} 2x \, dx = x^2 evaluated from 55 to 77.\newlineThe second integral is 571dx=x\int_{5}^{7} 1 \, dx = x evaluated from 55 to 77.\newlineFor the third integral, we need to split the fraction into two parts:\newline5721xx8dx573x8dx.\int_{5}^{7} \frac{21x}{x - 8} \, dx - \int_{5}^{7} \frac{3}{x - 8} \, dx.
  4. Simplify Third Integral Further: Simplify the third integral further.\newlineThe term 21xx8\frac{21x}{x - 8} can be rewritten as 21+168x821 + \frac{168}{x - 8} by polynomial long division.\newlineSo, 5721xx8dx=5721dx+57168x8dx\int_{5}^{7} \frac{21x}{x - 8} dx = \int_{5}^{7} 21 dx + \int_{5}^{7} \frac{168}{x - 8} dx.\newlineNow we have four integrals to evaluate:\newline572xdx\int_{5}^{7} 2x dx, 571dx\int_{5}^{7} 1 dx, 5721dx\int_{5}^{7} 21 dx, and 57168x83x8dx\int_{5}^{7} \frac{168}{x - 8} - \frac{3}{x - 8} dx.
  5. Evaluate Definite Integrals: Evaluate the definite integrals.\newlineThe first integral: 572xdx=x2\int_{5}^{7} 2x \, dx = x^2 evaluated from 55 to 77 = 7252=4925=247^2 - 5^2 = 49 - 25 = 24.\newlineThe second integral: 571dx=x\int_{5}^{7} 1 \, dx = x evaluated from 55 to 77 = 75=27 - 5 = 2.\newlineThe third integral: 5721dx=21x\int_{5}^{7} 21 \, dx = 21x evaluated from 55 to 77 = 5511.\newlineThe fourth integral: 5522.
  6. Evaluate Fourth Integral: Evaluate the fourth integral.\newlineThe fourth integral is 57165x8dx=165lnx8\int_{5}^{7} \frac{165}{x - 8} \, dx = 165 \cdot \ln|x - 8| evaluated from 55 to 77.\newlineThis gives us 165ln78165ln58=165ln1165ln3165 \cdot \ln|7 - 8| - 165 \cdot \ln|5 - 8| = 165 \cdot \ln|-1| - 165 \cdot \ln|-3|.\newlineSince the natural logarithm of a negative number is not defined in the real number system, we have made a mistake. We should have used the absolute value inside the logarithm.