Linear equations and changing the subject
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 7 practice questions, 1 real past-paper question with the answer explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- A balance
- One-step and two-step equations
Read the transcript of the teaching part
Last time
Before we start: last time, in Simultaneous equations, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
A balance
Imagine a set of scales. Whatever you do to one side, you must do to the other, or it tips over. That is the whole idea of solving an equation. Today you solve equations with brackets and fractions, form your own from words, and then rearrange formulae in exactly the same way.
One-step and two-step equations
To solve an equation, undo the operations in the opposite order to how they were applied. Take five x minus seven equals eighteen. The last thing done to x was minus seven, so undo it first: add seven to both sides. Then undo the multiplying by five: divide both sides by five. Always check by substituting back. Five times five is twenty-five, minus seven is eighteen. Correct.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Forming and solving equations · Rearranging formulae · Solving linear equations.
The whole chapter: Equations.
Chapter 10: Equations and formulae
- Linear equations and changing the subject 5 min
- Quadratic equations 6 min
- Simultaneous equations 6 min
Also for O Level Maths 4024
Which topics come up most in O Level Maths 4024 past papers, counted from every paper since 2004.