3x+y=21;y=4x

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2x+y=8
x+3y=14

Solution for 3x+y=21;y=4x system of equations: 


  • /| 3*x+y-21 = 0| y-(4*x) = 0
  • We try to solve the equation: 3*x+y-21 = 0
  • 3*x+y-21 = 0 // - 3*x-21
  • y = -(3*x-21)
  • y = 21-(3*x)
  • We insert the solution into one of the initial equations of our system of equations
  • We get a system of equations:
  • /| 21-(4*x)-(3*x) = 0| y = 21-(3*x)
  • 21-7*x = 0 // - 21
  • -7*x = -21 // : -7
  • x = -21/(-7)
  • x = 3
  • We insert the solution into one of the initial equations of our system of equations
  • For y = 21-(3*x): 
  • y = 21-(3*3)
  • y = 21-9
  • y = 12
  • We get a system of equations:
  • /| y = 12| x = 3

 

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