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15 (a) Factorise - OCR - GCSE Maths - Question 16 - 2023 - Paper 5

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15 (a) Factorise. 9x² - 4 (b) Solve by factorisation. 3x² - 2x - 8 = 0 (c) Solve. 2(x - 5) 1 - 3x = 2

Worked Solution & Example Answer:15 (a) Factorise - OCR - GCSE Maths - Question 16 - 2023 - Paper 5

Step 1

Factorise. 9x² - 4

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Answer

The expression is a difference of squares. We can factor it as follows:

9x24=(3x)2(2)2=(3x2)(3x+2)9x^2 - 4 = (3x)^2 - (2)^2 = (3x - 2)(3x + 2)

Step 2

Solve by factorisation. 3x² - 2x - 8 = 0

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Answer

First, we need to factor the quadratic equation. We look for two numbers that multiply to (3 * -8) = -24 and add to -2. These numbers are -6 and 4.

We can rewrite the equation as:

3x26x+4x8=03x^2 - 6x + 4x - 8 = 0

Now, we group the terms:

3x(x2)+4(x2)=03x(x - 2) + 4(x - 2) = 0

Factoring out the common term gives:

(3x+4)(x2)=0(3x + 4)(x - 2) = 0

Setting each factor to zero, we find the solutions:

  1. 3x+4=0x=433x + 4 = 0 \Rightarrow x = -\frac{4}{3}

  2. x2=0x=2x - 2 = 0 \Rightarrow x = 2

Step 3

Solve. 2(x - 5) 1 - 3x = 2

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Answer

Start by simplifying the equation:

2(x5)=2(13x)2(x - 5) = 2(1 - 3x)

Expanding both sides gives:

2x10=26x2x - 10 = 2 - 6x

Now, collect all terms involving x on one side and constant terms on the other:

2x+6x=2+102x + 6x = 2 + 10

This simplifies to:

8x=128x = 12

Now, solve for x:

x=128=32x = \frac{12}{8} = \frac{3}{2}

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