Elimination Systems What to Multiply

What is the proper set up to solve the equation?

-7x -2y= -13

x = 2y+11

• -7(11) -2y = -13

• -7(2y +11)-2y = -13

• -7x -2(11) =-13

• -7x - 2(2y+11)= -13

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve the system:

x+ 3y = 9

2x+ y = −2

• (3,2)

• (-2, 2)

• (3, -4)

• (-3, 4)

• (0.5, -3)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve for x and y
3x + 2y = 16
7x + y = 19

• (-2,5)

• (-2,-5)

• (2,-5)

• (2,5)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

To eliminate the x variables

• multiple the top equation by -1

• multiply the bottom equation by 4

• multiply the bottom equation by -4

• multiply the bottom equation by -1

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

To solve this by elimination, which of the follow answer choices show an accurate strategy that will eliminate a variable.

• Multiply the top equation by -3 and then add the equations together.

• multiply the top equation by -3 and multiply the bottom equation by +5. Then, add the equations together.

• multiply the top equation by +9 and multiply the bottom equation by -4. Then, add the equations together.

• multiply the top equation by 9 and multiply the bottom equation by 4. Then, add the equations together.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

If you add these equations together which variable is going to eliminate?

• x

• y

• 4

Answer explanation

-4x + 4x = 0x = 0

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

After you eliminate the x variables, you can solve for y.  Do it! What do you get?

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

To eliminate the y variable, . . .

• multiply the top equation by 1

• multiply the bottom equation by 3

• multiply the bottom equation by -3

• multiply the top equation by 4

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

To eliminate the y variable, . . .

• subtract the equations

• add the equations

• multiply the bottom equation by -1 and then add the equations together

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Once you find that y = -6, you can plug -6 in for y into either equation. Once you do this, simplify and solve for x. What do you get?

• x = 0

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6