#### Answer

not one-to-one

#### Work Step by Step

When we see $x^{2}$ in the function expression,
our first thought should be
"this is probably not one-to-one",
because, for example, $1^{2}=(-1)^{2}$...
$f(x)=-\sqrt{100-x^{2}}$
is defined for $x=1$ and $x=-1,$
(different values from the domain ...)
$f(1)=-\sqrt{99}=f(-1)$
( ... have the same function value)