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21 Write as a single fraction in its simplest form - OCR - GCSE Maths - Question 21 - 2020 - Paper 6

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21 Write as a single fraction in its simplest form. \[ \frac{x}{x + 1} + \frac{6x}{x + 2} - \frac{x - 2}{x^2 - 4} \]

Worked Solution & Example Answer:21 Write as a single fraction in its simplest form - OCR - GCSE Maths - Question 21 - 2020 - Paper 6

Step 1

Finding a Common Denominator

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Answer

The denominators are: ( x + 1 ), ( x + 2 ), and ( x^2 - 4 ) which can be factored as ( (x - 2)(x + 2) ). The least common denominator (LCD) is therefore ( (x + 1)(x + 2)(x - 2) ).

Step 2

Rewriting Fractions

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We will rewrite each fraction with the common denominator:

  1. ( \frac{x}{x + 1} = \frac{x(x + 2)(x - 2)}{(x + 1)(x + 2)(x - 2)} )
  2. ( \frac{6x}{x + 2} = \frac{6x(x + 1)(x - 2)}{(x + 1)(x + 2)(x - 2)} )
  3. ( \frac{x - 2}{x^2 - 4} = \frac{x - 2}{(x - 2)(x + 2)} = \frac{1}{x + 2} ) so we rewrite it as ( \frac{(x + 1)(x - 2)}{(x + 1)(x + 2)(x - 2)} ).

Step 3

Combining the Fractions

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Answer

Now we can add and subtract the numerators: [ \frac{x(x + 2)(x - 2) + 6x(x + 1)(x - 2) - (x + 1)(x - 2)}{(x + 1)(x + 2)(x - 2)} ]

Step 4

Simplifying the Numerator

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Answer

Expand and simplify the numerator:

  1. ( x(x + 2)(x - 2) = x(x^2 - 4) = x^3 - 4x )
  2. ( 6x(x + 1)(x - 2) = 6x(x^2 - x - 2) = 6x^3 - 6x^2 - 12x )
  3. Combine all these terms and simplify.

Step 5

Final Expression

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Answer

Finally, combine the simplified numerator with the common denominator: [ \frac{x^3 + 6x^3 - 4x - 6x^2 - 12x + x + 2}{(x + 1)(x + 2)(x - 2)} ] Combine like terms to get your final answer in simplest form.

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