1. Jun 2, 2013

### SweatingBear

I am stuck on this one:

According to me, the only correct answers are

$\vec{r} = \vec{t} - \vec{s} \\ \vec{r} + \vec{s} = \vec{t}$

But according to the key, these are also correct

$\vec{r} + \vec{t} = \vec{s} \\ \vec{s} + \vec{t} = \vec{r}$

I honestly do not see how, can somebody please explain?

2. Jun 2, 2013

### Staff: Mentor

Those are wrong, unless you have some special, weird vector spaces.

3. Jun 2, 2013

### CompuChip

However it does look like t - r = s.

4. Jun 2, 2013

### Staff: Mentor

That is another valid equation. t=r+s, r=t-s and s=t-r are equivalent.

5. Jun 2, 2013

Thanks.