Elimination with Systems of Equations

-2x + 6y = -20

2x + 5y = -11

what is the combined resulting equation?

• x + 11y = -31

• 11y = -31

• 11x = -31

• 4x + 11y = -31

• i need tutorials

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve using Elimination. Show your work!

2x - 6y = 20

2x + 5y = 53

• (3, 19)

• (19, 3)

• (-1, 73)

• (10, 0)

Answer explanation

2x - 6y = 20

2x + 5y = -11

We just need ONE of the 2x's to become -2x. So you can multiply equation 1 OR equation 2, but you can only change one of them so that you still get 2x & -2x to cancel.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

If solving with Elimination, which TWO first step options would NOT work?

x + y = 11

3x - 4y = -2

• Multiply Equation 1 by -3

• Multiply Equation 1 by 4

• Multiply Equation 2 by -3

• Multiply Equation 2 by -1

Answer explanation

x + y = 11

3x - 4y = -2

If we multiply Eq1 by -3 we will have -3x & 3x to cancel.

If we multiply Eq1 by 4 we will have 4y & -4y to cancel.

The other options would not give us two terms that are additive inverses.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve using Elimination. Show your work!

x + y = 11

3x - 4y = -2

• (6, 5)

• (2, -3)

• (7, 6)

• (6, 17)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

If using elimination to solve, which first step would NOT work?

x + 6y = 17

x - 3y = 8

• Multiply Equation 1 by -1

• Multiply Equation 1 by 2

• Multiply Equation 2 by -1

• Multiply Equation 2 by 2

Answer explanation

x + 6y = 17

x - 3y = 8

We could get rid of either x if we multiply 1 equation by -1 so that we have x & -x before adding.

We could get rid of y if we multiply equation 2 by 2 so that have 6y & -6y before adding.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

If using Elimination to solve, which variable is ready to be cancelled without using a multiplier?

3x + y = 19

2x - y = 6

• x

• y

Answer explanation

3x + y = 19

2x - y = 6

If we go ahead and add, the y's will cancel.

We would get

5x = 25

and could continue to solve.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

4x - 6y = -6

-2x -12y = -12

• (0,1)

• (1,0)

• (1,1)

• (2,1)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

-12x - 4y = -8

-6x - 2y = -4

• no solution

• (0,0)

• infinite solutions

• (4,0)

Tags

CCSS.8.EE.C.8B

2x + 3y = 12

5x - y = 13

• (-3 , -2)

• (1.5 , 2)

• (6 , 0 )

• (3 , 2)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve the system:

2x + 9y = -7

6x - 3y = 9

• (-1, -1)

• (2,-1)

• (1,1)

• (1,-1)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6