Function of the form `f(x)=(Q(x))/(P(x))=(a_0x^n+a_1x^(n-1)+...+a_(n-1)x+a_n)/(b_0x^m+b_1x^(m-1)+...+b_(m-1)x+b_m)`, where `Q(x)` and `P(x)` are polynomials is called rational function.
Domain of this function consists of all `x` such that `Q(x)!=0`.
Simple example of the rational function is `f(x)=(2x+1)/(x^2-x-2)=(2x+1)/((x-2)(x+1))`. Its domain is all `x` except `x=2` and `x=-1`.
This function is shown on the figure.