How do you solve #2x+9y=17#, #x=7-4y#?

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Answer 1 · 2017-02-25T12:44:31

x= -5
y= 3

Generally, you can solve linear systems in different ways:

1) Graphing

2) Substitution

3) Elimination.

In this case, since x is already isolated in the second equation, we would use substitution.

#2x + 9y = 17# Then we substitute #x = 7-4y#

#2(7-4y) + 9y = 17#

#14-8y + 9y = 17#

#y=3#

Then solve for x using either equation (I picked the second one)

#x = 7 - 4y#
#x = 7 - 4(3)#
#x = -5#