Expert: Abe Mantell - 5/28/2007

Question
I need to solve each system by graphing for example
3x-6y=9
x-2y=3

and

Find values for m and b in the following system so that the solution to the system
is (-3, 4).
5x +7y = b
mx +y = 22.

Answer
Hello Joanna,

3x-6y=9 & x-2y=3
It is tough for me to show here how to solve this by graphing.
I'll just briefly explain.  Sketch each line, as carefully as
you can, then see where they intersect...the x & y-coordinates.
You should notice that they are the same line, te 2nd is
3 times the first...thus they ntersect at infinitely many points.

As for the other problem.  Substitute (-3,4) into each,
then solve for b & m.  Thus, 5(-3)+7(4)=b so b=13 and
m(-3)+4=22, so that m=-6.

OK?

Abe