Evaluate the integral? : # int_3^4 (x^2-3x+6)/(x(x-2)(x-1)) dx#

Answer 1

# int_3^4 (x^2-3x+6)/(x(x-2)(x-1)) dx = 12ln2 -7ln3#

We first need to find the partial fraction decomposition of the integrand, which will be of the form;

# \ \ \ \ \ (x^2-3x+6)/(x(x-2)(x-1)) -= A/x + B/(x-2) + C/(x-1) # # :. (x^2-3x+6)/(x(x-2)(x-1)) = (A(x-2)(x-1) + Bx(x-1) + Cx(x-2)) /(x(x-2)(x-1))#

And so:

# :. x^2-3x+6 = A(x-2)(x-1) + Bx(x-1) + Cx(x-2) #
We can easily find the constants #A,B,C# by setting #x# to the specific values that make the denominator 0 or by comparing coefficients. (With practice this can be done instantly using the "Cover Up" method).
Put #x=0 => 6=A(-2)(-1) \ \ \ \ \ \ \ \ => A=3# Put #x=2 => 4-6+6=B(2)(1) \ \ \ \ \ => B=2# Put #x=1 => 1-3+6=C(1)(-1) => \ C=-4#
So the integral can be written as: # int_3^4 (x^2-3x+6)/(x(x-2)(x-1)) dx = int_3^4 3/x + 2/(x-2) -4/(x-1) dx#

Which we can now integrate as we know that

#d/dxln(ax+b)=a/(ax+b)#

Hence,

# int_3^4 (x^2-3x+6)/(x(x-2)(x-1)) dx = [3lnx+2ln|x-2| -4ln|x-1|]_3^4# # int_3^4 (x^2-3x+6)/(x(x-2)(x-1)) dx = (3ln4+2ln2 -4ln3)-(3ln3+2ln1-4ln2)# # int_3^4 (x^2-3x+6)/(x(x-2)(x-1)) dx = 3ln4+2ln2 -4ln3-3ln3-0+4ln2# # int_3^4 (x^2-3x+6)/(x(x-2)(x-1)) dx = 3ln4+6ln2 -7ln3# # int_3^4 (x^2-3x+6)/(x(x-2)(x-1)) dx = (2*3)ln2+6ln2 -7ln3# # int_3^4 (x^2-3x+6)/(x(x-2)(x-1)) dx = 12ln2 -7ln3# # int_3^4 (x^2-3x+6)/(x(x-2)(x-1)) dx ~~ 0.627480146042576#
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Answer 2

To evaluate the integral (\int_{3}^{4} \frac{x^2 - 3x + 6}{x(x - 2)(x - 1)} , dx), we can first perform partial fraction decomposition. After decomposing the fraction into simpler fractions, we can integrate each term separately. Then, we evaluate the integral over the given bounds.

The partial fraction decomposition of the given expression yields:

(\frac{x^2 - 3x + 6}{x(x - 2)(x - 1)} = \frac{A}{x} + \frac{B}{x - 2} + \frac{C}{x - 1})

Solving for (A), (B), and (C), we find (A = 2), (B = -1), and (C = 1).

So, the integral becomes:

(\int_{3}^{4} \left(\frac{2}{x} - \frac{1}{x - 2} + \frac{1}{x - 1}\right) , dx)

Integrating each term separately, we get:

(2\ln|x| - \ln|x - 2| + \ln|x - 1|)

Now, we evaluate this expression at the upper and lower bounds:

At (x = 4), we have:

(2\ln|4| - \ln|4 - 2| + \ln|4 - 1| = 2\ln(4) - \ln(2) + \ln(3))

At (x = 3), we have:

(2\ln|3| - \ln|3 - 2| + \ln|3 - 1| = 2\ln(3) - \ln(1) + \ln(2))

Therefore, the value of the integral is (2\ln(4) - \ln(2) + \ln(3) - 2\ln(3) + \ln(1) - \ln(2)). Simplifying, we get:

(2\ln\left(\frac{4 \cdot 3}{3^2}\right) - \ln(2) + \ln(3) - \ln(2))

This simplifies to:

(2\ln(2) - \ln(2) + \ln(3))

Combining the logarithms, we get the final result:

(\ln(2^2) + \ln(3) = \ln(4) + \ln(3) = \ln(12))

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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