Given the following system of equations, identify the type of system.
y = -x + 4
2x + 2y = 8
A. inconsistent
b. equivalent
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jimthompson5910 (jim_thompson5910):
are you able to solve 2x + 2y = 8 for y?
OpenStudy (anonymous):
i dont know how. van you explain?
jimthompson5910 (jim_thompson5910):
think of 2x+2y as 2y+2x
what operation will undo that +2x ?
OpenStudy (anonymous):
subtract 2 from both sides?
jimthompson5910 (jim_thompson5910):
2x actually
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jimthompson5910 (jim_thompson5910):
so we will have 2y = 8 - 2x which is the same as 2y = -2x + 8
jimthompson5910 (jim_thompson5910):
we want to isolate y fully
so we have to move that 2 (from 2y) over to the other side. How do we do this?
jimthompson5910 (jim_thompson5910):
hint: 2y means "2 times y"
OpenStudy (anonymous):
divide 2 from both sides?
jimthompson5910 (jim_thompson5910):
divide both sides by 2, yes
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jimthompson5910 (jim_thompson5910):
what do you get when you do this?
OpenStudy (anonymous):
y = -2x +4?
jimthompson5910 (jim_thompson5910):
you have to divide EVERY term by 2, not just the 8
OpenStudy (anonymous):
y=x+4?
jimthompson5910 (jim_thompson5910):
since it works like this
\[\Large 2y = -2x + 8\]
\[\Large \frac{2y}{2} = \frac{-2x + 8}{2}\]
\[\Large \frac{2y}{2} = \frac{-2x}{2} + \frac{8}{2}\]
\[\Large y = ??\]
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jimthompson5910 (jim_thompson5910):
x+4 is close, but no
OpenStudy (anonymous):
x+3?
jimthompson5910 (jim_thompson5910):
you had the +4 part correct
jimthompson5910 (jim_thompson5910):
the "x" part was incorrect
OpenStudy (anonymous):
why is x incorect?
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jimthompson5910 (jim_thompson5910):
you should divide -2x by 2 to get ????
OpenStudy (anonymous):
x?
jimthompson5910 (jim_thompson5910):
nope not x, you are thinking of 2x divided by 2
OpenStudy (anonymous):
isnt that the same thing??
OpenStudy (anonymous):
-x?
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jimthompson5910 (jim_thompson5910):
yes -x
jimthompson5910 (jim_thompson5910):
so we will have
y = -x + 4
jimthompson5910 (jim_thompson5910):
2x + 2y = 8 turns into y = -x + 4 when you solve for y
jimthompson5910 (jim_thompson5910):
so y = -x + 4 and 2x + 2y = 8 are equivalent (ie the same exact equations)
OpenStudy (anonymous):
thank you for your help
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