Substitution Method
Steps:
| 1) solve one of the equations for one of its variables |
| 2) substitute the expression from step 1 into the other equation and solve for the other variable |
| 3) substitute the value from step 2 into the orginal equation and solve |
Example: Solve the system of equations
3x + 4y = -4 equation 1
x + 2y = 2 equation 2
1) solve equation 2 for x
x + 2y = 2 write equaiton 2
x = -2y + 2 revised equation 2
2) substitute the expression for x into equation 1 and solve for y
3x + 4y = -4 write equation 1
3(-2y +2) + 4y =-4 substitute -2y + 2 for x
y = 5 solve for y
3) substitute the value of y into one of the orginal equations
x + 2y = 2 write the equation
x + 2 (5) = 2 plug in y
x = -8 solve
the answer is (-8,5)