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May 7th 2010, 01:27 PM
mojojojo

question.

http://img15.imageshack.us/img15/4735/camp.gif why cant you cancel the (-1)'s in this fraction? ...they just solved the problem.
May 7th 2010, 02:05 PM
Fohr

If you work it out:

2(-1)-1(4)
(-1)^2

is equal to -6. However if we cancel the (-1) on top so it's just 2(1) and cancel (-1)^2 to become just (-1) we get:

2(1)-1(4)
(-1)

which is 2. The problem is you have that " -1(4) " bit at the end. If it were just:

2(-1)
(-1)^2

Then you could definitely cancel the (-1). However, the " -1(4) " part screws it up! Hope this helps.
May 7th 2010, 02:34 PM
Bacterius

You can cancel it ! Look :

$\frac{2(-1) - 1(4)}{(-1)^2}$

$\frac{-2 - 4}{(-1)^2}$

$\frac{-(2 + 4)}{(-1)^2}$

$\frac{(-1)(2 + 4)}{(-1)^2}$

$\frac{2 + 4}{-1}$

$\frac{-(2 + 4)}{1}$

$-(2 + 4)$

$-2 - 4$

$-6$

Does it make sense ?
May 7th 2010, 02:43 PM
Fohr

Your math makes perfect sense. However, i believe mojojojo meant why can't you cancel the (-1)'s in the first step of the equation. Which you can not. Am i wrong?
May 7th 2010, 02:45 PM
Bacterius

Yes, you are right. One has to rearrange it and factorize it first before cancelling out the minus 1.

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