# X * 0=0

1. Jan 28, 2004

### Ed Quanta

I have to prove that x*0= 0 where x is any integer. I can do this pretty easily using the proposition that m(-1)=-m but I am not allowed to use this. In addition, I am unable to prove m(-1)=-m unless I accept the fact that anything times zero equals zero. Can anyone give me a hint or push on how to show this? I am just going around in circles.

2. Jan 28, 2004

### matt grime

0.m=(0+0).m =0.m+0.m

subtract m.0 from both sides.

3. Jan 28, 2004

### Ed Quanta

Thanks, Im an idiot. I kept trying to represent 0 as (m + -m)

4. Jul 19, 2009

### epkid08

When x is an integer, multiplication can be defined as:

$$x*a = \sum^x_{n=1} a$$

When a = 0:

$$x*0 = \sum^x_{n=1} 0 = \underbrace{0 + 0 + ... + 0}_x = 0$$

Last edited: Jul 19, 2009