B1. For the number $x$, it holds that: $x=\frac{1}{1+x}$. Calculate $x-\frac{1}{x}$. Simplify your answer as much as possible.
B1. -1 Given that $x=\frac{1}{1+x}$. We see that $x \neq 0$, because $0 \neq \frac{1}{1}$. We can therefore invert the fraction on both sides. This gives $\frac{1}{x}=1+x$. From this, it follows that $x-\frac{1}{x}=x-(1+x)=-1$.