1. G Dear ©2009 – Not to be sold/Free to use
Stage 5
Year 9
Simultaneous
Equations
Substitution
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G Dear ©2009 – Not to be sold/Free to use

2. The Substitution Method
1. Make one pronumeral the subject
2. Substitute into the other equation.
3. Solve this equation to find the value of one the variables.
4. Substitute the value into either of the original equations to find the other value.
5. Write as a co-ordinate pair.

3. The Substitution Method
y = 2x - 1
&
y = -x + 2
Substitute y
2x - 1 = -x + 2
Add x to both sides
y = 2x1-1
3x - 1 = 2
Add 1 to both sides
y = 1
3x = 3
x = 1
Simultaneous
Solution = (1,1)
Substitute x=1

4. The Substitution Method
2x - y + 1 = 0 & 3x – y - 1 = 0
+y y
2x + 1 = y
3x – (2x + 1) - 1 = 0
Make y the subject
y = 2x + 1
3x – 2x = 0
y = 2 x 2 + 1
Substitute y
x - 2 = 0
y = 5
x = 2
Simultaneous
Solution = (2,5)
Substitute x