Download Solving Systems of Equations: More on Substitution

Algebra I –Wilsen
Unit 6: Systems of Equations
Day Four
BLOCK 2
Solving Systems of Equations: More on Substitution
Sometimes, neither equation is in “x =” or “y =” format. In those cases, you have to put
one of the equations into “x =” or “y =” format yourself.
Example 1
–4x + 2y = –8
x+y=5
Step 1: Is there an equation already in “x =” or “y =” format?
If no, identify the simpler equation, then put it into “x =” or “y =” format.
Step 2: Take this entire expression and substitute it into the other equation.
Step 3: Take your value for y and substitute it into any equation to find x.
Choose whichever equation looks simplest!
The final solution is (
,
)
Example 2
2x + y = 2
5x + 3y = 5
Step 1: Is there an equation already in “x =” or “y =” format?
If no, pick an equation and solve for x or y. Choose the easiest option!
Step 2: Take your expression and substitute it into the other equation. Solve for the
variable.
Step 3: Take your answer and substitute it into any equation to solve for the other
variable. Choose whichever equation looks simplest!
The final solution is (
,
)
Solve each system of equations by substitution. SHOW ALL WORK! Remember, you
can check your answers!
1.
2.
x + 2y = 23
x + y = 13
The final solution is (
,
)
The final solution is (
,
)
3x – y = 16
x+y=4
3.
4.
x – 4y = – 6
y–x=3
The final solution is (
,
)
The final solution is (
,
)
2x + y = 7
4x – y = –1