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Evaluate 
int(x^(6)+2x^(4)+6x-9)/(x^(3)+3)dx
Choose 1 answer:
(A) 
(x^(4))/(4)+x^(2)-3x+C
(B) 
(x^(4))/(4)+x^(2)-9x+C
(C) 
(x^(4))/(4)+3x^(2)+3x+C
(D) 
(x^(4))/(4)+x^(2)+3x+C

Evaluate x6+2x4+6x9x3+3dx \int \frac{x^{6}+2 x^{4}+6 x-9}{x^{3}+3} d x \newlineChoose 11 answer:\newline(A) x44+x23x+C \frac{x^{4}}{4}+x^{2}-3 x+C \newline(B) x44+x29x+C \frac{x^{4}}{4}+x^{2}-9 x+C \newline(C) x44+3x2+3x+C \frac{x^{4}}{4}+3 x^{2}+3 x+C \newline(D) x44+x2+3x+C \frac{x^{4}}{4}+x^{2}+3 x+C

Full solution

Q. Evaluate x6+2x4+6x9x3+3dx \int \frac{x^{6}+2 x^{4}+6 x-9}{x^{3}+3} d x \newlineChoose 11 answer:\newline(A) x44+x23x+C \frac{x^{4}}{4}+x^{2}-3 x+C \newline(B) x44+x29x+C \frac{x^{4}}{4}+x^{2}-9 x+C \newline(C) x44+3x2+3x+C \frac{x^{4}}{4}+3 x^{2}+3 x+C \newline(D) x44+x2+3x+C \frac{x^{4}}{4}+x^{2}+3 x+C
  1. Divide and Sum Integrals: Divide x6x^6 by x3x^3 to get x3x^3, and 2x42x^4 by x3x^3 to get 2x2x. The integral becomes the sum of the integrals of x3x^3, 2x2x, rac{6x}{x^3+3}, and - rac{9}{x^3+3}.
  2. Integrate x3x^3: Integrate x3x^3 to get x44\frac{x^4}{4}.
  3. Integrate 2x2x: Integrate 2x2x to get x2x^2.
  4. Integrate 6xx3+3\frac{6x}{x^3+3}: Integrate 6xx3+3\frac{6x}{x^3+3}. This is a bit tricky, but notice that the derivative of x3+3x^3+3 is 3x23x^2, which is close to 6x6x. Let's use substitution: let u=x3+3u = x^3+3, then du=3x2dxdu = 3x^2 dx. We need to adjust for the 6x6x, so we multiply dudu by 23\frac{2}{3} to get the 6x6x. The integral of 6xx3+3\frac{6x}{x^3+3} becomes 6xx3+3\frac{6x}{x^3+3}22 times the integral of 6xx3+3\frac{6x}{x^3+3}33.
  5. Integrate 2duu2\frac{du}{u}: Integrate 2duu2\frac{du}{u} to get 2lnu.2\ln|u|.
  6. Substitute uu back: Substitute back for uu to get 2lnx3+32\ln|x^3+3|.
  7. Integrate 9/(x3+3)-9/(x^3+3): Integrate 9/(x3+3)-9/(x^3+3). This is a constant over a linear term, so it's just 9-9 times the integral of 1/(x3+3)1/(x^3+3). This doesn't have an elementary antiderivative, so it looks like I made a mistake here. The integral of 9/(x3+3)-9/(x^3+3) should be treated as a separate term.

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