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Solve x and y using the 'Elimination' method.

5x-4y=-4

2x-4y=-16

 Sep 19, 2019
 #1
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Solve the following system:
{5 x - 4 y = -4 | (equation 1)
2 x - 4 y = -16 | (equation 2)

 

Subtract 2/5 × (equation 1) from equation 2:
{5 x - 4 y = -4 | (equation 1)
0 x - (12 y)/5 = (-72)/5 | (equation 2)

 

Multiply equation 2 by -5/12:
{5 x - 4 y = -4 | (equation 1)
0 x+y = 6 | (equation 2)

Add 4 × (equation 2) to equation 1:


{5 x+0 y = 20 | (equation 1)
0 x+y = 6 | (equation 2)

Divide equation 1 by 5:


{x+0 y = 4 | (equation 1)
0 x+y = 6 | (equation 2)

 

x = 4       and        y = 6
 

 Sep 19, 2019
 #2
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Multiply first equation by  - 1 to get

-5x+4y=4     add this to the second equation to get

-3x=-12      so x = 4

Substitute this value of 'x' in to one of the equations to get 'y'

5(4)-4y = -4

20-4y =-4

-4y = -24    y = 6

 Sep 19, 2019

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