Simultaneous - Elimination SACHS
5x – y = 14
2x + y = 7
Solve by adding the equations.
=
5x – y = 14
2x + y = 7
Solve by adding the equations.
7x = 21
x =
2(
Sub in equation 1
5x – y = 14
2x + y = 7
) + y = 7
Solve by adding the equations.
7x = 21
x = 3
Sub in equation 1
5x – y = 14
2x + y = 7
6 + y = 7
Solve by adding the equations.
7x = 21
x = 3
y =
x +  y  =  3
x + 4y = 18
Solve by subtracting the equations.
=
x +  y  =  3
x + 4y = 18
Solve by subtracting the equations.
3y = 15
y =
Sub in equation 2
x +
x +  y  =  3
x + 4y = 18
Solve by subtracting the equations.
3y = 15
y = 5
= 3
Sub in equation 2
x +  y  =  3
x + 4y = 18
x + 5 = 3
Solve by subtracting the equations.
3y = 15
x =
y = 5
3x + 2y = 36
3x – 3y = 21
Solve by subtracting the equations.
=
[Spot the double negative]
3x + 2y = 36
3x – 3y = 21
Solve by subtracting the equations.
5y = 15
y =
3x + 2(
Sub in equation 1
3x + 2y = 36
3x – 3y = 21
Solve by subtracting the equations.
5y = 15
y = 3
) = 36
Sub in equation 1
3x + 2y = 36
3x – 3y = 21
Solve by subtracting the equations.
3x + 6 = 36
3x =
5y = 15
y = 3
Sub in equation 1
3x + 2y = 36
3x – 3y = 21
3x + 6 = 36
Solve by subtracting the equations.
3x = 30
5y = 15
y = 3
x =
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