SOLUTION: My sons homework can not figure out Solve Systems of Equations Algebraically here is the question y=-x y=-7x can you show me how to get answer?

Question 741070: My sons homework can not figure out Solve Systems of Equations Algebraically here is the question y=-x
y=-7x
can you show me how to get answer?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!

------------
These are equations of straight lines which
intersect at some point
--------------------
It's a good idea to see what you can about the
lines, just by looking at the equations.
The general form of a straight line is
where is the slope
of the lines. for both lines, so they
both look like
----------------------

The slope is
------------------

The slope is
-------------------
For the first equation, if I say
, then:

------------
For the 2nd equation, if I say
, then

---------------
I have just shown that both lines pass
through (0,0), which is the origin.
Two straight lines can only intersect at one point,
so, , is the solution
------------------------------------
Here is the plot of the lines:

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