My husband is a math tutor. He will love this!!! There is also a “proof” that shows that 1=0. That one was going around when I was in college. But, no, math is not truly evil – you just have to play by the rules.
Not to be a nerd or to state the obvious, but in the third line they have completely taken out a large number from each side. I could say more about what is wrong with it but I’ll stop there. Math isn’t evil just orderly and likes rules.
The problem is that you’ve done an illegal operation. You cannot take the square root of a negative number. When you take the square root of both sides (4th step), you are taking the square root of a negative number on the left side of the equation. Any math teacher will tell you that’s not allowed.
If you do the operations in the parentheses BEFORE taking the square root, you will get the correct answer.
P.S. I’m also a homeschool mom, but I was a math major in college.
I had to look at this a while. I think the problem is not that you are taking the square root of a negative number, since the square of a negative will be a positive, and therefore you can take the square root of it; it’s that the square root technically will be +1 or -1. Ordinarily you would just take the positive 1, but since the problem started with negative numbers, you need to list both as the answer to the square root. So the fallacy is in going from line 3 to line 4. In other words, you cannot state x=y just because x*x = y*y, because you must consider the sign.
1MamaHen
wrote on 25 February 2009 at 0:53
I personally have no idea what this is. Heaven help me!
2Faerylandmom
wrote on 25 February 2009 at 1:58
Math IS evil.
3Rachel
wrote on 25 February 2009 at 5:19
That doesn’t make any sense at all. I think it’s gotta be a misprint or something!
Nope. It actually makes perfect sense, albeit twisted and sinister.
4Catherine
wrote on 26 February 2009 at 2:11
My husband is a math tutor. He will love this!!! There is also a “proof” that shows that 1=0. That one was going around when I was in college. But, no, math is not truly evil – you just have to play by the rules.
Catherine
5Rachel
wrote on 26 February 2009 at 2:52
Ok. You HAVE to explain this or you’ll break my brain!
6Jenny
wrote on 27 February 2009 at 13:00
Not to be a nerd or to state the obvious, but in the third line they have completely taken out a large number from each side. I could say more about what is wrong with it but I’ll stop there. Math isn’t evil just orderly and likes rules.
7Kate
wrote on 28 February 2009 at 4:11
I love math! Always have!
8Sylvia
wrote on 23 April 2009 at 4:34
The problem is that you’ve done an illegal operation. You cannot take the square root of a negative number. When you take the square root of both sides (4th step), you are taking the square root of a negative number on the left side of the equation. Any math teacher will tell you that’s not allowed.
If you do the operations in the parentheses BEFORE taking the square root, you will get the correct answer.
P.S. I’m also a homeschool mom, but I was a math major in college.
9Gretchen
wrote on 16 May 2009 at 2:21
I had to look at this a while. I think the problem is not that you are taking the square root of a negative number, since the square of a negative will be a positive, and therefore you can take the square root of it; it’s that the square root technically will be +1 or -1. Ordinarily you would just take the positive 1, but since the problem started with negative numbers, you need to list both as the answer to the square root. So the fallacy is in going from line 3 to line 4. In other words, you cannot state x=y just because x*x = y*y, because you must consider the sign.
Math major in a previous life here too