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Unformatted text preview: Finally, plug this into either of the equations and solve for x. We will use the first equation this
© 2007 Paul Dawkins 320 http://tutorial.math.lamar.edu/terms.aspx College Algebra time. 2 x + 4 ( -4 ) = -10
2 x - 16 = -10
2x = 6
So, the solution to this system is x = 3 and y = -4 .
[Return to Problems] There is a third method that we’ll be looking at to solve systems of two equations, but it’s a little
more complicated and is probably more useful for systems with at least three equations so we’ll
look at it in a later section.
Before leaving this section we should address a couple of special case in solving systems. Example 3 Solve the following systems of equations.
x- y =6
-2 x + 2 y = 1
We can use either method here, but it looks like substitution would probably be slightly easier.
We’ll solve the first equation for x and substitute that into the second equation. x = 6+ y -2 ( 6 + y ) + 2 y = 1
-12 - 2 y + 2 y = 1
- 12 = 1 ??
So, this is clearly not true and there doesn’t appear to be a mistake anywhere in our work. So,
what’s the problem? To see let’s graph these two lin...
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- Spring '12