MathematicsClass 8Linear Equations in One Variable

Solving Equations with Variables on Both Sides

Applying balancing methods to isolate variables present on both sides of a linear equation.

Class 8 · MathematicsCBSE & ICSE SOF IMO

Definition

These are linear equations that contain the same variable term on both sides of the equals sign. To solve them, you must use transposition to collect all variable terms on one side and all constant terms on the other side. Once grouped, simplify both sides and isolate the variable to find its value.

Key formula

ax + b = cx + d

Worked examples

1

Solve 3x - 2 = 2x + 1: Subtract 2x from both sides to get x - 2 = 1, then add 2 to get x = 3.

2

Solve 5p - 3 = 3p + 5: Transpose 3p to the left and -3 to the right to get 2p = 8, so p = 4.

3

Solve 2y + 5 = 7 - y: Transpose -y to get 3y = 2, yielding y = 2/3.

Common mistakes

  • Forgetting to change the sign of a term when transposing it across the equals sign.
  • Attempting to isolate constants and variables on opposite sides simultaneously without proper grouping.
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