Year 9–10 Maths — Number, Algebra and Equations
Year 9–10 algebra extends into quadratic equations, surds and more complex equation solving. These are the skills VCE Maths Methods assumes from day one — arriving in Year 11 with gaps here makes Unit 1 very difficult.
Key Concepts & Formulas
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Index laws: aᵐ × aⁿ = aᵐ⁺ⁿ; aᵐ ÷ aⁿ = aᵐ⁻ⁿ; (aᵐ)ⁿ = aᵐⁿ; a⁰ = 1; a⁻ⁿ = 1/aⁿ; a^(1/n) = ⁿ√a
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Expanding: (a + b)² = a² + 2ab + b²; (a − b)² = a² − 2ab + b²; (a + b)(a − b) = a² − b²
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Factoring: look for common factors first; then difference of squares; then factoring quadratic ax² + bx + c
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Quadratic formula: x = (−b ± √(b² − 4ac)) / 2a — use when factoring is difficult
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Completing the square: convert x² + bx + c to (x + b/2)² + (c − b²/4)
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Surds: √a × √b = √(ab); √a / √b = √(a/b); rationalising the denominator: multiply by √a/√a
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Like surds: 3√2 + 5√2 = 8√2; unlike surds (e.g. √2 and √3) cannot be combined
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Simultaneous equations: substitution or elimination to find values satisfying both equations
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Linear-quadratic simultaneous equations: substitute the linear into the quadratic → solve the resulting quadratic
Practice Questions
5 questionsAttempt each question before reading the hint. These are styled to match school assessment format.
Q1.Factorise fully: 2x² − 8x − 24.
2 marksShow hint
Take out the common factor first.
Q2.Solve x² − 5x + 6 = 0 by factoring and verify using the quadratic formula.
3 marksQ3.Simplify: √48 − 2√3.
2 marksQ4.Solve simultaneously: y = 2x + 1 and y = x² − x + 3.
4 marksQ5.Simplify (3 + √5)(3 − √5) and (1 + √2)².
3 marksCommon Mistakes to Avoid
These are the errors that students most frequently make in Number, Algebra and Equations — and that examiners are specifically watching for.
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(a + b)² = a² + 2ab + b² — forgetting the middle term: (a + b)² ≠ a² + b²
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Forgetting the ± in the quadratic formula — there are usually two solutions
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Rationalising incorrectly — multiply numerator AND denominator by the surd
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In linear-quadratic systems, stopping after finding x-values without substituting back to find y-values
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