Thread

Math puzzle...kinda

MacNN Troubleshooting 6 posts Jul 5, 2004 to Jul 5, 2004

#1 Mon, 5 Jul 2004 - 15:42 MacNN

X=15
Y=13

X=Y+2
X(X-Y)=(Y+2)(X-Y)
X^2-XY=XY-Y^2+2X-2Y
X^2-XY-2X=XY-Y^2-2Y
X(X-Y-2)=Y(X-Y-2)

X=Y ->15=13

What went wrong

(N.B.: X^2 is X square)

#2 Mon, 5 Jul 2004 - 15:51 MacNN

That's why I prefer art.

#3 Mon, 5 Jul 2004 - 15:51 MacNN

i'm not really sure (summer vacation so my brain is effectively turned off) but (x - y - 2) = 0, so x(x - y - 2) = y(x - y - 2) is correct, since 0 = 0.

do i get a cookie?

#4 Mon, 5 Jul 2004 - 16:15 MacNN

The problem is that you're dividing by 0

#5 Mon, 5 Jul 2004 - 17:53 MacNN

The answer is X=Y=Err: Div by 0

#6 Mon, 5 Jul 2004 - 22:54 MacNN

Whenever you divide an equality by a variable, you have to determine the domain of the new equality. In this case, the domain of the new equality is all X and Y such that X-Y-2 does not equal 0.

Thus, X = Y if and only if X does not equal Y + 2.

Unfortunately, X DOES equal Y + 2, so X can never equal Y.