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# My /. fortune is mistaken

#### Quantum Jim (UID: 610382) writes | more than 5 years ago

4

My /. fortune was:

(1) X=Y ; Given
(2) X^2=XY ; Multiply both sides by X
(3) X^2-Y^2=XY-Y^2 ; Subtract Y^2 from both sides
(4) (X+Y)(X-Y)=Y(X-Y) ; Factor
(5) X+Y=Y ; Cancel out (X-Y) term
(6) 2Y=Y ; Substitute X for Y, by equation 1
(7) 2=1 ; Divide both sides by Y
-- "Omni", proof that 2 equals 1

My /. fortune was:

(1) X=Y ; Given
(2) X^2=XY ; Multiply both sides by X
(3) X^2-Y^2=XY-Y^2 ; Subtract Y^2 from both sides
(4) (X+Y)(X-Y)=Y(X-Y) ; Factor
(5) X+Y=Y ; Cancel out (X-Y) term
(6) 2Y=Y ; Substitute X for Y, by equation 1
(7) 2=1 ; Divide both sides by Y
-- "Omni", proof that 2 equals 1

However, you can only cancel out the (X-Y) if X != Y because if they are equal then the expression is zero! Indeed, the rest of the steps can be left, so you end up with:

2(x-y) = (x-y)
0 = 0

Friends don't let friends divide by zero!

### hey there... (1)

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#### tuxette (UID: 731067) | more than 5 years ago

long time no see... how's the BJJ going?

### Re:hey there... (1)

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#### Quantum Jim (UID: 610382) | more than 6 years ago

Hey, BJJ is going good. I got promoted to blue, won a few tournaments, and am half way to purple I think. How's the krav maga going along? I have been pretty busy and haven't been around for a while. Hopefully I have some more free time now...

### Re:hey there... (1)

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#### tuxette (UID: 731067) | more than 6 years ago

Sounds great! Krav Maga is going fine, except I have this finger injury that is really cramping my style :-( I hope it's better in time for grading in June...

### Re:hey there... (1)

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#### Quantum Jim (UID: 610382) | more than 6 years ago

Good luck with your grading. I always buddy-tape injured fingers and toes. Even when not training, the buddy tape helps it heal faster.
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