Solving systems by substitution lesson

Multiple Choice

Solve for y

10x - 2y = 18

• y = 5x + 20

• y = -10x - 16

• y = -5x - 9

• y = -2x + 28

2x + 3y = 12

Steps For Solving By Substitution

Step 1: Pick an equation

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Step 2: ​When solving a system with 2 equations. Pick 1 equation and get x OR y by itself.

x=___ or y=____​

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​Step 3: Substitute x =___ or y = ___ from the first step into the other equation and solve for the variable.

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Step 4: Substitute your answer into one of the original equations and solve for the other variable.

3x + 2y = 16
7x + y = 19

Multiple Choice

x - 3y = -13
4x + 2y = 4

• (1, 4)

• (-1, -4)

• (-1, 4)

• (1, -4)

Try:

​y=2x + 1

​and 3x+y=11

​Equations:

y= -4x + 8 y= -3x+5

Multiple Choice

Solve this system of equations. 
y = 2x + 1
y = 4x - 1

• (1,3)

• (-1,-3)

• (-1,3)

• (3,1)

C5L3 Solving Systems of Equations

Special Cases

• If the systems results in a true statement, then there is infinitely many solutions

   ex. 5=5

• Infinitely Many Solutions Example: -4x+2y=-10 and y=2x-5

• If the systems results in a false statement, then there is   no solution

   ex. 4=0

• No Solution Example: 3x-3y=5 and x= -4+y