Integrating to find area under a graph

How to use integration to find the area under a curve. 

Special notes:  

- Sometimes integration gives a negative answer, so ignore the negative.  

- Areas below the x-axis should be done separately to areas above the x-axis

- For more complex questions, use a two-step technique to take away the area under the curve from the whole shape.

Practice Questions:

http://www.myimaths.com/tasks/library/alevel/lib/loadTask.asp?title=alevel/core2/Integration/integration4AreaNegOH&taskID=2057