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

1 Answer
Nicolas
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.

For more info, Click on that video

Related questions
See all questions in Systems Using Substitution
Impact of this question
2519 views around the world
You can reuse this answer
Creative Commons License