How do you find the solution set for x+9y=-1, 2x+4y=5?

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Answer 1 · 2015-08-06T10:59:59

#{(x = 7/2), (y=-1/2) :}#

You could solve this system of equations by suing the substitution method.

To do that, use the first equation to write #x# as a function of #y#

#x + 9y = -1#

#x = -1 - 9y#

Now use this expression in the second equation - this will get you the value of #y#

#2x + 4y = 5#

#2 * (-1-9y) +4y = 5#

#-2 - 18y + 4y = 5#

#-14y = 7 implies y = 7/(-14) = color(green)(-1/2)#

FInally, use the value of #y# to get the value of #x#

#x = -1 - 9 * (-1/2)#

#x = -1 + 9/2 = color(green)(7/2)#