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Find the value of \[\int_{2}^{2} \frac{6x + 1}{6x^{2} - 7x + 2} \; dx,\] expressing your answer in the form \(mln 2 + nln 3\), where \(m\) and \(n\) are integers. - AQA - A-Level Maths Mechanics - Question 6 - 2019 - Paper 3

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Find-the-value-of-\[\int_{2}^{2}-\frac{6x-+-1}{6x^{2}---7x-+-2}-\;-dx,\]-expressing-your-answer-in-the-form-\(mln-2-+-nln-3\),-where-\(m\)-and-\(n\)-are-integers.-AQA-A-Level Maths Mechanics-Question 6-2019-Paper 3.png

Find the value of \[\int_{2}^{2} \frac{6x + 1}{6x^{2} - 7x + 2} \; dx,\] expressing your answer in the form \(mln 2 + nln 3\), where \(m\) and \(n\) are integers.

Worked Solution & Example Answer:Find the value of \[\int_{2}^{2} \frac{6x + 1}{6x^{2} - 7x + 2} \; dx,\] expressing your answer in the form \(mln 2 + nln 3\), where \(m\) and \(n\) are integers. - AQA - A-Level Maths Mechanics - Question 6 - 2019 - Paper 3

Step 1

Use partial fractions with linear denominators

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Answer

To evaluate the integral, we first express the integrand using partial fractions:

[\frac{6x + 1}{6x^{2} - 7x + 2} = \frac{A}{3x - 1} + \frac{B}{2x - 2}]

Multiplying through by the denominator (6x^{2} - 7x + 2), we can solve for constants (A) and (B).

Step 2

Obtain the correct numerators

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Answer

Expanding:

[6x + 1 = A(2x - 2) + B(3x - 1)]

Setting (x = 1) will help us find (A) and (B):

Solving gives:

  • When (x = 1): (6(1) + 1 = A(0) + B(3(1) - 1)) leads to finding (B).

  • Additionally, set up another equation using another value for (x) to find (A).

Step 3

Obtain partial fractions completely correct

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Answer

For the values of (A) and (B), use substitution to get:

  • Final partial fraction form is obtained from constants derived.

Step 4

Integrate 'their' partial fractions

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Answer

Now, integrate the resulting fractions:

[\int \left( \frac{A}{3x - 1} + \frac{B}{2x - 2} \right)dx]

Apply integral rules, yielding:

[A \ln |3x - 1| + B \ln |2x - 2| + C]

Step 5

Substitute limits into 'their' integral

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Answer

Apply the limits from 2 to 2:

[A \ln |3(2) - 1| + B \ln |2(2) - 2| - (A \ln |3(2) - 1| + B \ln |2(2) - 2|)]

Step 6

Correct final answer in correct form

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Answer

The result in the form (mln 2 + nln 3) will yield integer values for (m) and (n) when simplifying the logarithmic results.

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