GCSE Maths (Edexcel)

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Solving by Substitution

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Algebra Solving Equations and Inequalities

Solving by Substitution

7:03 Simultaneous Equations
Spec A19
Previous Approximating Solutions with Graphs Next Deriving Simultaneous Equations
  • Simultaneous equations can be solved by making a variable the subject of one equation and substituting it into the other.
  • The solution to simultaneous equations is the values of x and y that satisfy both equations at the same time.
  • One way to solve simultaneous equations is by substitution, where one variable is substituted into the other equation.
  • The choice of which variable to make the subject or whether to use elimination instead of substitution is up to the solver.
  • To solve for x, substitute the expression for x into the second equation and simplify.
  • Solve the new equation in terms of y to find the value of y.
  • Substitute the value of y back into the first equation to solve for x.
  • The full solution contains both the value for x and the value for y.
  • Double check the solution by substituting the values back into one of the original equations.

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