When drawing a graph such as f(x) you pretty much only need to find the points for where f(x)=0 and the maxima and minima and then draw the lines between these.
For example, you could solve f(x)=0 by using the quadratic equation. To find the maxima and minima you can dervivate the function and find f'(x)=0.
f(x)=x^2+1 does not have any points for where the function is zero. But it has a minimal point located at (0,1) which can be found through f'(x)=0.
Since it's harder to know how the graph is illustrated without the points where f(x)=0, and without maxima and minima we can add a table for the graph. Which we can do with a set of random x values. In order to see the f(x) values at the x values.
You can view a method for this here.
