The Graphs of General Polynomial Functions

Compared with the graph of f(x)=axn,the following also hold true.

  • The graph of f(x)=axnis reflected across the x-axis.
  • The graph of f(x)=axn+kis translated (shifted) k units up if k>0 and kunits down if k<0.
  • The graph of f(x)=a(xh)nis translated (shifted) h units to the right if h>0 and hunits to the left if h<0.
  • The graph of f(x)=a(xh)n+kshows a combination of these translations.

Examples

Graph each polynomial function. Determine the largest open intervals of the domain over which each function is increasing or decreasing.

  1. f(x)=x52
  2. f(x)=(x+1)6
  3. f(x)=2(x1)3+3

Solutions

  1. f(x)=x52

    The graph will be the same shape as that of f(x)=x5,but translated 2 units down. This function is increasing on its entire domain (,).
    Graph of the function.PNG

  2. f(x)=(x+1)6
    In f(x)=(x+1)6, the function has a graph with the same shape as f(x)=x6, but since x+1=x(1), it is translated 1 unit to the left. This function is decreasing on ( ,1] and increasing on [1,).
    Graph of this sixth degree function.PNG
  3. f(x)=2(x1)3+3
    The negative sign in -2 causes the graph of the function to be reflected across the x-axis when compared with the graph of f(x)=x3. Because 2∣>1, the graph is stretched vertically when compared to the graph of f(x)=x3. It is also translated 1 unit right and 3 units up. This function is increasing on its entire domain (,).
    Graph of third degree polynomial function.PNG

    Domain & Range of Polynomial Functions

    Unless otherwise restricted, the domain of a polynomial function is the set of all real numbers. Polynomial functions are smooth, continuous curves on the interval (,). The range of a polynomial function of odd degree is also the set of all real numbers.