A function is a special relationship where each input has a single output. It is often written as $y=f(x)$ where $x$ is input and $y$ is the output value. Say $x_1,x_2∈D$ $f(x_1)=f(x_2)$ if $x_1=x_2$ or, $f(x_1)≠f(x_2)$ if $x_1≠x_2$ then the function is called a one-to-one function. Where D is the set of decimal numbers. ifRead More