Y=-x-1 y=-2x+1 ?

2 Answers
Mar 9, 2018

#2=x#

Explanation:

Substitute the #-x-1# for #y# to get

#-x-1=-2x+1#

Add #x# to #-x# and #-2x# to get

#-1=-1x+1#

Subtract #1# from #1# and #-1# to get

#-2=-1x#

Divide both sides by #-1# to get

#2=x#

Mar 9, 2018

Linear algebra states that x=2, making y=-3

Explanation:

Linear algebra allows us to add and subtract whole equations from each other, like so:

#y=-2x+1#
#-#
#ul(y=-x-1)#
#0=-x+2#

Taking the solution from the bit of linear algebra we've done:
#0=-x+2 rArr color(red)(x=2)#

We can now plug our solution for #x# back into either of the equations and solve for #y#:

#y=-(2)-1 rArr y=-2-1 rArr color(red)(y=-3)#
#y=-2(2)+1 rArr y=-4+1 rArr color(red)(y=-3)#