Solving Simultaneous Equations

Students learn how to set up and solve a pair of simultaneous equations using the elimination method.  Learning progresses from solving equations where the coefficients are equal to setting up a pair of equations with different coefficients from known facts.

This unit takes place in Term 2 of Year 11 and follows on from solving equations with a single unknown.

Solving Simultaneous Equations Lessons

Revision Lessons

Prerequisite Knowledge

  • Solve two simultaneous equations in two variables algebraically;
  • Find approximate solutions to simultaneous equations in two variables using a graph
  • Translate simple situations or procedures into algebraic expressions or formulae; derive an equation

Success Criteria

  • Solve two simultaneous equations in two variables algebraically;
  • Find approximate solutions using a graph

Key Concepts

  • For every unknown an equation is needed.
  • Students need to have a secure understanding of adding and subtracting with negatives when eliminating an unknown.
  • Coefficients need to be equal in magnitude to eliminate an unknown.
  • Students need to check their solutions by substituting the calculated values into the original equations.

Common Misconceptions

  • Students often struggle knowing when to add or subtract the equations to eliminate the unknown. Review addition with negatives to address this.
  • Equations need to be aligned so that unknowns can be easily added or subtracted. If equations are not aligned students may add or subtract with non like variables.
  • Students often try to eliminate variables with their coefficients being equal

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