How do you solve the system of equations #y= - 8# and #9x - 5y = - 5# using substitution?

1 Answer
smendyka
Mar 13, 2017

See the entire solution process below:

Explanation:

Because the first equation is already solved for #y# we know the #y# solution for this system of equations. Additionally, we can substitute #-8# for #y# in the second equation and calculate #x#:

#9x - 5y = -5# becomes:

#9x - (5 xx -8) = -5#

#9x - (-40) = -5#

#9x + 40 = -5#

#9x + 40 - color(red)(40) = -5 - color(red)(40)#

#9x + 0 = -45#

#9x = -45#

#(9x)/color(red)(9) = -45/color(red)(9)#

#(color(red)(cancel(color(black)(9)))x)/cancel(color(red)(9)) = -5#

#x = -5#

The solution is: #x = -5# and #y = -8# or #(-5, -8)#

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