WAEC 2013 Mathematics · Question 35

Express 2x+3−1x−2\frac{2}{x + 3} - \frac{1}{x - 2} as a simple fraction

Options

  1. A.x−7x2+x−6\frac{x - 7}{x^2 + x - 6}
  2. B.x−1x2+x−6\frac{x - 1}{x^2 + x - 6}
  3. C.x−2x2+x−6\frac{x - 2}{x^2 + x - 6}
  4. D.x−27x2+x−6\frac{x - 27}{x^2 + x - 6}

Answer: A. x−7x2+x−6\frac{x - 7}{x^2 + x - 6}

Explanation written with AI and checked against the answer key

Step 1: Analyze the question We need to combine two fractions with different denominators into one fraction.

Step 2: Concept Use the common denominator (x + 3)(x − 2).

Step 3: Solution

2x+3−1x−2=2(x−2)−1(x+3)(x+3)(x−2)\frac{2}{x+3} - \frac{1}{x-2} = \frac{2(x-2) - 1(x+3)}{(x+3)(x-2)}

Expand the numerator:

  • 2(x − 2) = 2x − 4
  • 1(x + 3) = x + 3

Numerator: 2x − 4 − x − 3 = x − 7

Expand the denominator: (x + 3)(x − 2) = x² − 2x + 3x − 6 = x² + x − 6

Result=x−7x2+x−6\text{Result} = \frac{x-7}{x^2+x-6}

Step 4: Answer

Tip: When subtracting fractions, put the minus sign in front of the whole second numerator. Many students forget to change the sign of the 3 in (x + 3), writing 2x − 4 − x + 3 instead of 2x − 4 − x − 3. Use brackets to avoid this error.

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