Systems by Elimination

What do you need to do first when solving a system by elimination?

• Arrange the equations so the variables, equal signs, and constants line up.
• Arrange the coefficients in ascending order.
• Arrange the constants in randomized order.
• Arrange the coefficients in descending order.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

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

2x + 2y = -2

3x - 2y = 12

• you cannot solve this using eliminiation

• cross out the 2x and 3x

• cross out the 2y and -2y

• change to slope intercept form and graph

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

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

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

When you add the two equations, what is the answer?
2x + 3y = 9
-5x - 3y = -21

• 3x = -12
• 7x + 6y = 30
• -3x = 12
• -3x = -12

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What is the value of x in the system below?
2x + 3y = 9
-5x - 3y = -21
-3x        = -12
       x = ?

• 24
• -4
• 4
• 1/4

Tags

CCSS.HSA.REI.C.9

Have you found the solution the the system we have been working on?

• No - the work never ends.
• No - we need to find the y coordinate.
• Yes x=4.  What else is there in life?
• SQUIRREL

Tags

CCSS.8.EE.C.8B

Given that x = 4, how will we find the value of y in this systems of equations.
2x + 3y = 9
5x + 3y = 21

• Choose one the equations, ignore the x variable, and solve for y.
• Substitute x into one the equations and solve.
• Sit and whine until the answer magically appears on my paper.
• Cheat off my neighbor.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Which equation below shows the correct way to solve for y in the system given x = 4?
2x + 3y = 9
5x + 3y = 21

• 2(4) + 3y = 9
  the only way to go.
• 5(4) + 3y = 21
  It's my way or the highway.
• Both of those could give you the y value.
• Why find y?

4x + 8y = 20

-4x + 2y = -30

• (-7,1)

• (2,-5)

• (-2,5)

• (7,-1)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

x - y = 11

2x + y = 19

• (10,-1)

• (-1,10)

• (3,-4)

• (6,7)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6