X-y=7 X+y=10 In linear combination?

1 Answer
Jun 20, 2018

#x=8.5,y=1.5#

Explanation:

Given:

  • #x-y=7#

  • #x+y=10#

Adding the first equation to the second equation, we get:

#x-color(red)cancelcolor(black)y+x+color(red)cancelcolor(black)y=7+10#

#2x=17#

#:.x=17/2=8.5#

Now, you can substitute #x# into any of the two equations to find #y#. Note that the value of #y# found should be the same in both cases, otherwise you've made a mistake. I always like to substitute into the first equation.

Substituting #x# into the first equation, we get:

#8.5-y=7#

#:.-y=7-8.5#

#=-1.5#

#:.y=1.5#