Solving Systems by Elimination and Subtraction

Which method would be best for solving the system shown?

• Substitution

• Elimination by addition

• Elimination by subtraction

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

The school that Stefan goes to is selling tickets to a choral performance. On the first day of ticket sales the school sold 3 senior citizen tickets and 1 child ticket for a total of $38. The school took in $52 on the second day by selling 3 senior citizen tickets and 2 child tickets. Which equations represents the system that could be used?

• 1s + 3c = 38
  2s + 3c = 52

• 3s + 1c = 38
  3s + 2c = 52

• s + c = 38
  s + c = 52

• 3s + 3c = 38
  1s + 2c = 52

Tags

CCSS.HSA.CED.A.3

What is the solution?

• (1, -1)

• (-1, 1)

• (0, -2)

• (0, 1)

Tags

CCSS.8.EE.C.8B

What is the solution to the system?

• (0, 3)

• (1, -1)

• (-3, 1)

• (1, 3)

Answer explanation

The lines intersect at (1,3) so that is the solution.

Tags

CCSS.8.EE.C.8B

Which variable would be easiest to eliminate?

• x

• y

• Neither

Answer explanation

The terms with x in them have opposite coefficients (4x and -4x), so they will be the easiest to eliminate when we add the equations together.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve the following using elimination.

• (10,-1)

• (-1,10)

• (-1,-10)

• (-10,-1)

Answer explanation

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

To Find the solution to this system of equations, Juan decided to multiply the entire first equation by -1. What method is Juan employing to find the solution?

• Substitution

• Graphing

• No Solution

• Elimination

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What is the first step in solving a system of equations by elimination?

• Rewrite the equations so the variables are all on the same side and line up the like terms.

• Get both equations in slope-intercept form.

• Get both equations equal to zero.

• Put the x terms first.

Answer explanation

We need all of the variables on the same side so that we can eventually add the left side of both equations together and add the right side of both equations together.

If the variables aren't on the same side of the equal-sign, then we can't combine like terms.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

-4x - 6y = 6
4x + 6y = -4

• no solution

• (2,0)

• (-4,0)

• (0,0)

Tags

CCSS.8.EE.C.8B

Solve by elimination
-6x + 5y = 1
6x + 4y = -10

• (1,-1)

• (0,-1)

• (1,1)

• (-1,-1)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6