Simultaneous Equations: Equal Values and Substitution Method
Learn how to solve simultaneous equations using the Equal Values method and the Substitution method. Letβs get started! π

Video Lesson
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Flashcards
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ποΈ Equal Values Method
- Make the same variable (like y) the subject in both equations.
- Set the two expressions equal and solve for x.
- Substitute the x value back to find y.
ποΈ Substitution Method
- Rearrange one equation to express one variable in terms of the other, for example y = x β 1.
- Substitute this into the other equation so it has only one variable, then solve.
- Exam tip: always substitute both values back into the original equations to check.
ποΈ Choosing the Right Method
- Use equal values when the same variable is easy to make the subject.
- Use substitution when one equation is easy to rearrange to remove one variable.
- Both methods give the same solution for x and y.
Practice Questions
Test your understanding
We have the following simultaneous equations. Do , satisfy this simultaneous equation?
Correct! π +10 pointsNot quite right
Substituting and into both equations shows that both equations are satisfied: and . Therefore, and is the solution to the simultaneous equations.
We have the following simultaneous equations. Do , satisfy this simultaneous equation?
Correct! π +10 pointsNot quite right
Substituting and gives , which is correct, but , which is not 8. Therefore, and do not satisfy the simultaneous equations.
Solve the simultaneous equations:
Correct! π +20 pointsNot quite right
Add the two equations together: , which simplifies to , so . Substituting into gives . Therefore, the solution is .
Solve the simultaneous equations:
Correct! π +20 pointsNot quite right
Set the two expressions for equal to each other: . Solving for gives . Substituting into gives . Therefore, and is the solution.
Solve the simultaneous equations:
Correct! π +20 pointsNot quite right
Substitute into the second equation: . This simplifies to , so and . Substituting back gives . Therefore, the solution is .
Solve the simultaneous equations:
Correct! π +30 pointsNot quite right
Rearrange the second equation to get . Substitute this into the first equation: . Simplifying gives , so and . Substituting back gives . Therefore, the solution is .
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Interactive Activity
Solve simultaneous equations step-by-step using equal values and substitution
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