How do you solve y=3x-9 and 2y-6x=-18 using substitution?

1 Answer
Jul 17, 2017
  • First you regroup them (so that substitution is easier)

y=3x-9
2y-6x=-18

  • Name the equations (again for easier substitution)

y=3x-9 rarr color(blue)1
2y-6x=-18 rarr color(red)2

  • Sub color(blue)1 in color(red)2

2(3x-9)-6x=-18

  • Then solve

2(3x-9)-6x=-18
6x-18-6x=-18
6x-6x=-18+18
0=0

As you may have realised, those simultaenous equations are undefined. Try checking if you got any errors while copying this question.

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