## Precalculus (6th Edition)

A function $f$ is a one-to-one function if different values of the domain correspond to different values of the range. ---------- When we see $($... x ...$)^{2}$ in the function expression, our first thought should be "this is probably not one-to-one", because, for example, $1^{2}=(-1)^{2}$... We can get 1 in the parentheses if x=0 and $-1$ if $x=-2.$ So, for two different values from the domain, $0$ and $-2$... $f(0)=2(1)^{2}-6=-4$ $f(-2)=2(-1)^{2}-6=-4$ ... we have the same function value.