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Equations!


Date: 2 May 1995 07:40:45 -0400
From: Milli Kutuphane
Subject: (none)
  
x+y=5
xy=3  
x^2+y^2=?


Date: 2 May 1995 11:13:06 -0400
From: Dr. Sydney
Subject: Re: Equations!!

Hello!  

There are a couple of ways to approach this problem...  I'll give you a few
hints, and then you can see if you can take it from there, okay?

First, what if you squared both sides of the first equation?  Write out 
                        (x +y)^2 = 5^2 
and then see if you can see something that will help you solve the problem.

A more conventional way of doing the problem would be to first solve for x
and then solve for y (or first solve for y and then solve for x).  Rewrite
the first equation as y = 5 - x.  Now Substitute this y in the second
equation.  Now your second equation has only x's in it, and you should be
able to solve for x.  Once you have x, figure out what y is, and then plug
those numbers into the third equation and see what you get!  

I tend to think the first way of doing it is neater, just because it
involves less work and has sort of a trick involved, but either way will get
you the answer you want.  If you have any questions about this, write back!

--Sydney, "Dr. Math"
    
Associated Topics:
Middle School Equations

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