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Express $$\frac{5(x - 3)}{(2x - 11)(4 - 3x)}$$ in the form $$\frac{A}{(2x - 11)} + \frac{B}{(4 - 3x)}$$ where A and B are integers. - AQA - A-Level Maths Mechanics - Question 5 - 2021 - Paper 2

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Express--$$\frac{5(x---3)}{(2x---11)(4---3x)}$$-in-the-form--$$\frac{A}{(2x---11)}-+-\frac{B}{(4---3x)}$$-where-A-and-B-are-integers.-AQA-A-Level Maths Mechanics-Question 5-2021-Paper 2.png

Express $$\frac{5(x - 3)}{(2x - 11)(4 - 3x)}$$ in the form $$\frac{A}{(2x - 11)} + \frac{B}{(4 - 3x)}$$ where A and B are integers.

Worked Solution & Example Answer:Express $$\frac{5(x - 3)}{(2x - 11)(4 - 3x)}$$ in the form $$\frac{A}{(2x - 11)} + \frac{B}{(4 - 3x)}$$ where A and B are integers. - AQA - A-Level Maths Mechanics - Question 5 - 2021 - Paper 2

Step 1

Form the identity/equation

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Answer

To express 5(x3)(2x11)(43x)\frac{5(x - 3)}{(2x - 11)(4 - 3x)} in the required form, we write: 5(x3)A(43x)+B(2x11)5(x - 3) \equiv A(4 - 3x) + B(2x - 11).

Step 2

Obtain A = -1

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Answer

To find A and B, we can select an appropriate value for x. Let's substitute x=43x = \frac{4}{3} into the equation:

5(433)A(4343)+B(24311).5\left(\frac{4}{3} - 3\right) \equiv A(4 - 3 \cdot \frac{4}{3}) + B(2 \cdot \frac{4}{3} - 11). This simplifies to (5(-\frac{5}{3}) \equiv A(0) + B(-\frac{5}{3})$$ which gives us A = -1 after solving for it.

Step 3

Obtain B = 1

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Answer

Next, let's substitute x=112x = \frac{11}{2} into the original equation:

5(1123)A(43112)+B(211211).5\left(\frac{11}{2} - 3\right) \equiv A(4 - 3 \cdot \frac{11}{2}) + B(2 \cdot \frac{11}{2} - 11). After simplification, we find that A = -1 leads to B = 1 after appropriate calculations.

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