Are the following functions one-to-one?

? Yes No 1. $\displaystyle f(x) = x^{2}+4$

? Yes No 2. $\displaystyle f(x) = \left|x-2\right|$

? Yes No 3. $\displaystyle f(x) = 5x+4$

? Yes No 4. $\displaystyle f(x) = \frac{1}{x}$