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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 Pure - 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 Pure-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 Pure - Question 5 - 2021 - Paper 2

Step 1

Form the identity

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Answer

We start by writing the expression in the form of the equation:

5(x3)(2x11)(43x)=A(2x11)+B(43x)\frac{5(x - 3)}{(2x - 11)(4 - 3x)} = \frac{A}{(2x - 11)} + \frac{B}{(4 - 3x)}.

Multiplying both sides by the denominator, we get:

5(x3)=A(43x)+B(2x11)5(x - 3) = A(4 - 3x) + B(2x - 11).

Step 2

Obtain A

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Answer

To find A, we can substitute a convenient value for x.

Letting ( x = \frac{4}{3} ), the equation simplifies as follows:

5(433)=A(43(43))+B(2(43)11)5\left(\frac{4}{3} - 3\right) = A(4 - 3\left(\frac{4}{3}\right)) + B(2\left(\frac{4}{3}\right) - 11).

Simplifying, we find: ( A = -1 ).

Step 3

Obtain B

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Answer

Next, to find B, we substitute a different value for x.

Letting ( x = \frac{11}{2} ), we again simplify:

5(1123)=A(43(112))+B(2(112)11)5\left(\frac{11}{2} - 3\right) = A(4 - 3\left(\frac{11}{2}\right)) + B(2\left(\frac{11}{2}\right) - 11).

Which results in:\n( B = 1 ).

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