Now, you need some practice.

1. Solve using elimination: Set of two equations: 3x+4y = 16; 4x - 2y = -2

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The system is ready for elimination as it is. If we add both equations, the 2y and the -2y form a zero pair and are eliminated from the resulting equation.

Add the two equations, then divide both sides of the equation by 7.

Find the value of y by substituting 2 in for x in one of the original equations. I chose the first equation because every term was positive.

Replace x with 2
Simplify
Subtract 6 from both sides of the equation
Simplify
Divide both sides of the equation by 2
Simplify

Check the accuracy of your point by substituting in both 2 and 5 into the 2nd equation—the equation that we did not use to find y.

Since -2 is what we were supposed to get, we did the work correctly.

The solution to the system is (2, 5).

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2. Solve using elimination : set of two equations: x-4y=-17; 3x+5y=0

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The system needs to be prepared for elimination because just adding the two equations right now would not eliminate a variable. You first want to look through the equation to see if any of the coefficients for the variables is 1. Since x in the first equation fits this request, x is the variable that we will eliminate. Close Pop Up
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The system needs to be prepared for elimination because just adding the two equations right now would not eliminate a variable. You first want to look through the equation to see if any of the coefficients for the variables is 1. Since x in the first equation fits this request, x is the variable that we will eliminate.

We will need to multiply the first equation by -3. Why? To make a zero pair, the coefficients for the variable must be the same number but with opposite signs. Since the coefficient of x in the second equation is 3, we need to change the coefficient of x in the first equation to -3 (its opposite). We make this change through multiplication.


Find the value of x by substituting 3 in for y in one of the original equations. I chose the second equation because of the smaller numbers

Check the accuracy of your point by substituting in both -5 and 3 into the first  equation—the equation that we did not use to find x.

      (-5) – 4(3) =
-5  – 12  = -17      Since -17 is what we were supposed to get, we did the work correctly.

The solution to the system is (-5, 3).

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If you would like to see how the elimination method is used in solving some real-world problems, click here.