3x+9y=21;2x+8y=18

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Remember to put linear equations with variables x and y.
for example:
2x+y=8
x+3y=14

Solution for 3x+9y=21;2x+8y=18 system of equations: 


  • /| 3*x+9*y-21 = 0| 2*x+8*y-18 = 0
  • We try to solve the equation: 3*x+9*y-21 = 0
  • 3*x+9*y-21 = 0 // - 3*x-21
  • 9*y = -(3*x-21) // : 9
  • y = (-(3*x-21))/9
  • y = (21-(3*x))/9
  • We insert the solution into one of the initial equations of our system of equations
  • We get a system of equations:
  • /| 8*((21-(3*x))/9)+2*x-18 = 0| y = (21-(3*x))/9
  • (8*(21-3*x))/9+2*x-18 = 0
  • 56/3-2/3*x-18 = 0
  • 2/3-2/3*x = 0
  • 2/3-2/3*x = 0 // - 2/3
  • -2/3*x = -2/3 // : -2/3
  • x = -2/3/(-2/3)
  • x = 1
  • We insert the solution into one of the initial equations of our system of equations
  • For y = (21-(3*x))/9: 
  • y = (21-(1*3))/9
  • y = (21-3)/9
  • y = 18/9
  • y = 2
  • We get a system of equations:
  • /| y = 2| x = 1

 

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