Many thanks for this I have implemented all of your comments except the first I ahve altered the explanation about values of solutions to make it I hope clearer just what I mean I have managed to alter the diagrams as you suggest using Inkscape which I downloaded a few days ago I would welcome your help pages about this as my first attempts at creating diagrams were unsuccessful all the lines text etc whihc I created came out in light grey rather than black even though I set it at black using the fill so either I am doing something very stupid or there is some setting which I am missing I am now going to make the page live Thanks again