Question

Why is f not a function from R to R if

a) f(x)=1x?


f(x) is not well-defined because there are two distinct values assigned to each x.
f(0) is not defined.
f(x) is not defined for x<0.


b) f(x)=x−−√x?


f(0) is not defined.
f(x) is not defined for x<0.
f(x) is not well-defined because there are two distinct values assigned to each x