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AQA GCSE Maths (8300) · Algebra
Mini-Lesson

Algebra

This mini-lesson covers the Algebra strand of AQA GCSE Maths (8300): expanding & factorising, solving linear and quadratic equations, simultaneous equations, rearranging formulae, sequences (nth term), straight-line graphs y = mx + c, and inequalities.

y = mx + cm = gradient (steepness)  ·  c = y-intercept (where it crosses the y-axis)

These games test recall of facts, formulae and methods — not full multi-step working. Answer the questions as you go and collect ⭐ stars. Press Start when you're ready.

Expanding brackets

Expanding brackets

To expand, multiply everything inside the bracket by the term outside. For two brackets, multiply every term in the first by every term in the second (FOIL).

Worked example — single

3(2x + 5) = 3×2x + 3×5 = 6x + 15

Worked example — double

(x + 3)(x + 4) = x² + 4x + 3x + 12 = x² + 7x + 12

Common slip: forgetting the middle terms. (x + 3)(x + 4) is not x² + 12 — you must add the two cross-terms 4x + 3x = 7x.

Calculate

Your turn — expand

1Expand (x + 5)(x + 2) to give x² + bx + 10. Type the value of b (the coefficient of x).
Hint: the x-terms are 2x and 5x, which add to give bx.
Factorising

Factorising quadratics

Factorising is the reverse of expanding. For x² + bx + c, find two numbers that multiply to c and add to b.

Worked example

Factorise x² + 7x + 12.

Need two numbers: product 12, sum 7 → 3 and 4.

= (x + 3)(x + 4)

Difference of two squares: x² − 9 = (x + 3)(x − 3). It has no middle term because +3x and −3x cancel.

Calculate

Your turn — factorise

2x² + 9x + 20 = (x + 4)(x + p). Type the value of p.
Hint: 4 × p = 20 and 4 + p = 9.
Solving linear equations

Solving linear equations

Do the same operation to both sides to keep the equation balanced, undoing operations in reverse (inverse) order until x is alone.

Worked example

Solve 3x + 7 = 22.

Subtract 7: 3x = 15

Divide by 3: x = 5

Check: substitute back — 3×5 + 7 = 22 ✓. Always a fast way to catch a slip.

Calculate

Your turn — solve for x

3Solve 5x − 4 = 31. Type the value of x.
Hint: add 4 to both sides (5x = 35), then divide by 5.
Solving quadratic equations

Solving quadratics

To solve x² + bx + c = 0, factorise, then set each bracket to zero. On Higher, use the quadratic formula:

x = [−b ± √(b² − 4ac)] ÷ 2afor ax² + bx + c = 0
Worked example

Solve x² + 7x + 12 = 0.

Factorise: (x + 3)(x + 4) = 0

So x + 3 = 0 or x + 4 = 0 → x = −3 or x = −4

Sign trap: if (x + 3) = 0 then x = −3, not +3. The solutions are the values that make each bracket zero.

Quick check

Roots of a quadratic

?What are the solutions of (x − 2)(x + 5) = 0?
Simultaneous equations

Simultaneous equations

Two equations, two unknowns. Eliminate one variable by adding or subtracting the equations (after matching coefficients), then back-substitute.

Worked example

Solve x + y = 10 and x − y = 4.

Add the equations: 2x = 14 → x = 7

Substitute: 7 + y = 10 → y = 3  (so x = 7, y = 3)

Check both: 7 + 3 = 10 ✓ and 7 − 3 = 4 ✓. Your pair must satisfy both equations.

Calculate

Your turn — simultaneous

4Solve 2x + y = 13 and x + y = 8. Type the value of x.
Hint: subtract the second from the first to eliminate y: (2x + y) − (x + y) = 13 − 8.
Rearranging formulae

Rearranging (changing the subject)

Rearranging a formula uses the same balancing rules as solving an equation — do inverse operations to both sides until the required letter is the subject.

Worked example

Make r the subject of C = 2πr.

Divide both sides by 2π:

r = C ÷ (2π)

Tip: whatever is "attached" to the letter you want, undo it. Here r is multiplied by 2π, so you divide by 2π.

Calculate

Your turn — substitute

5Using v = u + at, work out v when u = 4, a = 3 and t = 5.
Hint: v = 4 + 3×5 = 4 + 15.
Sequences · nth term

The nth term of a linear sequence

For an arithmetic sequence, the nth term is: (common difference)×n + (adjust to term 0).

nth term = dn + (a − d)d = common difference, a = first term
Worked example

Sequence: 5, 8, 11, 14, …

Common difference d = 3, so start with 3n.

3×1 = 3, but first term is 5, so add 2 → nth term = 3n + 2

Check: put n = 4 into 3n + 2 → 14 ✓, the 4th term.

Calculate

Your turn — nth term

6The nth term of a sequence is 4n − 1. Work out the 10th term.
Hint: substitute n = 10: 4×10 − 1.
Straight-line graphs

Straight-line graphs: y = mx + c

Every straight line has equation y = mx + c. The gradient m = rise ÷ run; c is where the line crosses the y-axis.

c run rise m = rise ÷ run
Positive gradient rises left to right; c fixes the height where x = 0.

Parallel lines have the same gradient m. On Higher, perpendicular gradients multiply to −1.

Quick check

Read off the gradient

?What is the gradient of the line y = 3x − 7?
Match game

Match: bracket form ⇄ expanded

Tap a factorised expression on the left, then its correct expanded form on the right.

Inequalities

Solving inequalities

Solve an inequality just like an equation — but there's one special rule: multiplying or dividing by a negative flips the sign.

<   ≤   >   ≥less than · at most · greater than · at least
Worked example

Solve 2x + 1 < 9.

Subtract 1: 2x < 8

Divide by 2 (positive, no flip): x < 4

The flip rule: if you divide by −2, e.g. −2x < 6 becomes x > −3. The inequality sign reverses.

Calculate

Your turn — inequality

7Solve 3x − 2 > 13. The solution is x > k. Type the value of k.
Hint: add 2 (3x > 15), then divide by 3.
Sort it

Linear or quadratic?

A linear expression has x to the power 1 (a straight line); a quadratic contains an x² term (a curve). Tap an expression, then the box it belongs in.

📏 Linear

📈 Quadratic

Recap

The whole Algebra strand

Expand: multiply out brackets (FOIL for doubles); factorise is the reverse.

Linear equations: do the same to both sides until x is alone.

Quadratics: factorise then set each bracket = 0; or use the quadratic formula.

Simultaneous: eliminate a variable, then back-substitute.

Rearrange: change the subject with inverse operations.

Sequences: nth term = dn + (a − d) for a linear sequence.

Graphs: y = mx + c — gradient m, intercept c; parallel lines share m.

Inequalities: solve like equations, but flip the sign when ÷ or × by a negative.

You've covered every Algebra sub-topic in AQA 8300. Press Finish to see your score.

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Mini-lesson complete!

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