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Simultaneous Linear Equations

The Substitution Method

This method involves making one variable the subject of an equation, and substituting it into the other equation to obtain an equation with a single variable.

Example 3.

Here it was easy to first make y the subject of Equation 2, as the coefficient of y is 1. We could still solve the problem in this way even if the coefficient of y was not 1, it would just involve more algebra and possibly fractional coefficients. If Equation 1 had a y coefficient of 1, it would be best to make y the subject of equation 1 and then substitute into Equation 2. Similarly, if x had a coefficient of 1 in either equation, you could rearrange that equation to make x the subject of the equation and the substitute for x in the other equation. To see some examples of these, click the "More" link below.

More Examples (this will open in another window)

Exercise 3.

Now practice with a few of these exercises:

<< The Elimination Method | Simultaneous Linear Equations Index | Geometric or Graphical Interpretation >>