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Quadratic Equations - Edexcel GCSE Higher Maths

Typically 5-8 marks across the three papers · Spec 1MA1

Quadratic equations are equations with an x2x^2 term, and on Edexcel's 1MA1 Higher tier you are expected to solve them three ways: factorising (spec ref A18), the quadratic formula, and completing the square, plus using them inside problems about areas, graphs and the Higher-only quadratic simultaneous equations.

Edexcel typically gives factorising questions in the middle of a paper for 3 marks, while formula and completing-the-square questions appear later, often asking for answers 'to 2 decimal places' (a strong hint to use the formula) or 'in the form (x+a)2+b(x+a)^2 + b'. The quadratic formula is not printed on 1MA1 papers, so it has to be memorised, a genuine difference from some other boards' support materials.

Examiners' reports repeatedly flag the same losses: candidates who divide through by xx and lose a root, sign slips inside the formula when bb is negative, and answers left unfinished at (x3)(x+2)(x-3)(x+2) without stating the solutions. Every question below is built to practise the full 'solve and state both roots' habit.

Worked example

Solve 2x27x+3=02x^2 - 7x + 3 = 0
[3 marks]
  1. Look for a factorisation of 2x27x+32x^2 - 7x + 3: the outer/inner pairs must add to 7x-7x, giving (2x1)(x3)(2x - 1)(x - 3).
    M1: brackets that expand to give two correct terms
  2. Set each bracket to zero: 2x1=02x - 1 = 0 or x3=0x - 3 = 0.
    M1: using the factorised form to create two equations
  3. State both solutions: x=12x = \frac{1}{2} and x=3x = 3. A quick check: 2(14)72+3=02(\frac{1}{4}) - \frac{7}{2} + 3 = 0
    A1: both roots, including the fractional one

Practice questions

Original questions in Edexcel 1MA1 Higher style. Factorising questions are fair game on non-calculator Paper 1, and give exact fractions where they arise (type 1/2). Remember the quadratic formula is not printed on Edexcel papers, so practise recalling it before you need it.

No account needed: the questions below are always free to check, plus 8 extra questions today. Your score so far updates as you go.

  1. Question 1 Warm-up [1 mark]
    Which of these is the correct factorisation of x2x12x^2 - x - 12?
    Answer options for question 1
  2. Question 2 Warm-up [2 marks]
    Expand and simplify (x+3)(x4)(x + 3)(x - 4)
  3. Question 3 Exam pace [3 marks]
    Solve 2x25x3=02x^2 - 5x - 3 = 0 Give exact answers.
  4. Question 4 Exam pace [2 marks]
    x2+6x+2x^2 + 6x + 2 can be written in the form (x+a)2+b(x + a)^2 + b. Find the value of bb.
  5. Question 5 Stretch [3 marks]
    Solve x26x+2=0x^2 - 6x + 2 = 0. Give the larger solution correct to 2 decimal places.
  6. Question 6 Stretch [4 marks]
    A rectangle has length xx cm and width (x3)(x - 3) cm. Its area is 40 cm240 \text{ cm}^2. Find the value of xx.

Common mistakes examiners see

  • Dividing both sides by xx in equations like x24x=0x^2 - 4x = 0, which silently throws away the root x=0x = 0.

    Never divide by the unknown. Factorise instead: x(x4)=0x(x - 4) = 0 gives both x=0x = 0 and x=4x = 4.

  • Sign errors substituting a negative bb into the quadratic formula, such as writing b-b as 7-7 when b=7b = -7.

    Write the substitution line in full with brackets before evaluating: x=(7)±(7)24(2)(3)2(2)x = \frac{-(-7) \pm \sqrt{(-7)^2 - 4(2)(3)}}{2(2)}. Edexcel awards the method mark for exactly this line.

  • Stopping at the factorised form (x3)(x+2)=0(x - 3)(x + 2) = 0 without stating the solutions.

    The question says solve, so the final line must be values of xx. Factorising alone leaves the accuracy marks on the table.

  • Halving bb incorrectly (or forgetting to subtract the square) when completing the square on x2+6x+2x^2 + 6x + 2.

    Follow the two-step routine every time: (x+3)2(x + 3)^2 deals with x2+6xx^2 + 6x, then subtract 323^2 and bring back the constant: (x+3)27(x + 3)^2 - 7.

  • Rounding answers when the question asked for exact values, or giving 1 decimal place when it asked for 2.

    Match the answer format to the instruction word for word: 'exact' means surds or fractions, '2 d.p.' means use the formula and keep intermediate digits.

Frequently asked questions

Is the quadratic formula given on Edexcel GCSE papers?
No. Edexcel 1MA1 papers do not print the quadratic formula, so Higher-tier students must memorise x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} and be ready to use it whenever a quadratic will not factorise.
How do I know which method Edexcel wants?
Read the answer format: 'solve' with whole-number-friendly coefficients suggests factorising; 'give your answers to 2 decimal places' signals the formula; 'write in the form (x+a)2+b(x+a)^2+b' is completing the square. Marks are awarded for any valid method unless the form is specified.
Do quadratic equations appear on the non-calculator paper?
Yes. Factorisable quadratics and completing the square are regularly set on Paper 1, where surd and fraction answers must be left exact. Formula questions needing decimal answers sit on the calculator papers.