Solving Systems of Equations by Elimination with Multiplication

Solve the system by elimination.

−6x + 6y = 0

9x − 8y = 4

• (4, −9)

• Infinite number of solutions

• (−9, 4)

• (4, 4)

________________ are two or more equations that have the same variables and work together.

• graphing lines

• elimination method

• system of equations

• table

Nancy went to the grocery story.  On Monday she purchased 4 apples and 6 bananas for a total of $13.  On Wednesday she purchased 3 apples and 7 bananas for a total of $13.50.  Which system of equations represents the situation?

• 4x + 6y = 3
  13.5x - 13y = 6

• x + y = 4
  x - y = 6

• 4x + 6y = 13
  3x + 7y = 13.5

• 4x - 6y = 13
  3x - 7y = 13.5

Homer sells tickets for admission to your school play and collects a total of $104. Admission prices are $6 for adults and $4 for children. He sold 21 tickets total. Solve the system:
x + y = 21
6x + 4y = 104

• (10, 11)

• (12, 9)

• (11, 10)

• (9, 12)

Solve by elimination:
7x-9y=29

7x+2y=-15

• (-4,-1)

• (-1.-4)

• (-1,4)

• (-1,6)

Solve by elimination:
7x+y=-9

-3x-y=5

• No solution

• (1,8)

• (-2,-3)

• (-1,-2)

Solve by elimination 
2x+9y= -7 
6x-3y= 9 

• (-1, -1) 

• (2,-1)

• (1,1)

• (1,-1)

What would be the first step in finding the solution with elimination?

4x + 3y = 1

x - 3y = -11

• cross out the 3y and -3y

• cross out the 4x and x

• change all the signs of the second equation

• add 1 and -11

What is the next step in solving this system by elimination?
2x + 3y = 9
5x + 3y = 21

• Nothing - it is ready to go.

• Multiply one equation by -1

• Multiply the top equation by 3.

• Multiply the bottom equation by 7.

Solve the system:
x + 6y = 17
x - 3y = 8

• (5, 2)

• (11, 1)

• (1, 11)

• no solution