Cancelling the Signs in Algebra

[adjacent]

Homework Statement

This is the simplest problem you would ever get.
$\frac{-fu}{s-f}=\frac{fu}{-s+f}$
This is true.
So the signs can be cancelled.What are the rules for doing that?
I guess I was not listening to the teacher when I first learned algebra.

The Attempt at a Solution

Don't think that I don't know algebra.I just want to know the rules of THAT.

 

[Tanya Sharma]

Homework Statement

This is the simplest problem you would ever get.
$\frac{-fu}{s-f}=\frac{fu}{-s+f}$
This is true.
So the signs can be cancelled.What are the rules for doing that?
I guess I was not listening to the teacher when I first learned algebra.

The Attempt at a Solution

Don't think that I don't know algebra.I just want to know the rules of THAT.

Multiplying numerator and denominator of a rational number by a non zero number keeps it unchanged .The non zero number in this case is -1.

 

[adjacent]

Ok.Thanks,
I never thought I would not know something thing like that. :)