Prove that f(x)=1x2f(x) = \frac{1}{x^2}f(x)=x21 is not one-to-one on R∖{0}\mathbb{R} \setminus \{0\}R∖{0}.
f(−2)=f(2)=1/4f(-2) = f(2) = 1/4f(−2)=f(2)=1/4
fff is decreasing
fff is discontinuous
fff is always positive