Subjects calculus

Integral Evaluation Eb6Edf

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Integral Evaluation Eb6Edf


1. **State the problem:** Evaluate the definite integral $$\int_0^b \frac{3x^3 - x^2 + 2x - 4}{\sqrt{x^2 - 3x + 2}} \, dx$$ where the upper limit $b$ is unspecified. 2. **Analyze the integrand:** The denominator is $$\sqrt{x^2 - 3x + 2}$$. Factor the quadratic inside the square root: $$x^2 - 3x + 2 = (x-1)(x-2)$$. The expression under the root is positive where $x < 1$ or $x > 2$. 3. **Simplify the integral:** Rewrite the integral as $$\int_0^b \frac{3x^3 - x^2 + 2x - 4}{\sqrt{(x-1)(x-2)}} \, dx$$. Since the integral is from 0 to $b$, and the denominator is real only outside the interval [1,2], the integral is defined for $b \leq 1$ or $b \geq 2$. 4. **Substitution:** Let us try to simplify the denominator by substitution. Set $$t = \sqrt{(x-1)(x-2)}$$. Alternatively, consider the substitution to express the denominator in a simpler form or use partial fractions for the numerator. 5. **Partial fraction decomposition of numerator:** Try to express numerator in terms of $(x-1)$ and $(x-2)$: Since denominator involves $(x-1)(x-2)$, write numerator as $$3x^3 - x^2 + 2x - 4 = A(x-1)(x-2) + B(x-1) + C(x-2) + D$$ or use polynomial division. 6. **Polynomial division:** Divide numerator by $x^2 - 3x + 2$: Divide $3x^3 - x^2 + 2x - 4$ by $x^2 - 3x + 2$: - Leading term: $3x^3 / x^2 = 3x$ - Multiply divisor by $3x$: $3x^3 - 9x^2 + 6x$ - Subtract: $(3x^3 - x^2 + 2x - 4) - (3x^3 - 9x^2 + 6x) = 0 + 8x^2 - 4x - 4$ - Next term: $8x^2 / x^2 = 8$ - Multiply divisor by 8: $8x^2 - 24x + 16$ - Subtract: $(8x^2 - 4x - 4) - (8x^2 - 24x + 16) = 0 + 20x - 20$ Remainder: $20x - 20$ So, $$\frac{3x^3 - x^2 + 2x - 4}{x^2 - 3x + 2} = 3x + 8 + \frac{20x - 20}{x^2 - 3x + 2}$$ 7. **Rewrite the integral:** $$\int_0^b \frac{3x^3 - x^2 + 2x - 4}{\sqrt{x^2 - 3x + 2}} \, dx = \int_0^b (3x + 8) \sqrt{x^2 - 3x + 2} \, dx + \int_0^b \frac{20x - 20}{\sqrt{x^2 - 3x + 2}} \, dx$$ 8. **Substitute $u = x^2 - 3x + 2$:** Then, $$du = (2x - 3) dx$$ Rewrite the integrals accordingly. 9. **Evaluate each integral separately:** - For $$\int (3x + 8) \sqrt{u} \, dx$$, express $x$ in terms of $u$ or use substitution. - For $$\int \frac{20x - 20}{\sqrt{u}} \, dx$$, express in terms of $u$ and $du$. 10. **Final answer:** The integral can be expressed in terms of $u$ and evaluated accordingly. Since the upper limit $b$ is unspecified, the integral is left in terms of $b$. **Summary:** The integral simplifies to $$\int_0^b (3x + 8) \sqrt{(x-1)(x-2)} \, dx + \int_0^b \frac{20(x - 1)}{\sqrt{(x-1)(x-2)}} \, dx$$ which can be evaluated by substitution and standard integral techniques depending on the value of $b$. This completes the evaluation steps for the given integral.