powell991 powell991
  • 01-02-2017
  • Mathematics
contestada

solve the linear system using substitution.
4x - y =5
4x + 4y = -4

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togunsile2008 togunsile2008
  • 01-02-2017
4x - y =5 
4x + 4y = -4

Change all the signs of the first equation
-4x + y = -5
Add 4x to both sides
y == 4x - 5

Substitute for y in second equation

4x + 4(4x - 5) = -4

4x + 16x - 20 = -4

20x - 20 = -4

Add 20 to both sides

20x = 16

Divide both sides by 20

x = 16/20 === 4/5

Substitute to find y

y == 4x - 5 == 4(4/5) - 5 == 16/5  - 5 =  -9/5

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