(x+10)(x-10)

This can be written as the difference of two squares:  x² - 10² or x² - 100.

alan when i solved this out my answer is totally different!im geting 2x^2 as my answer !

Well, let's do it in detail:

(x + 10)(x - 10) = x*(x-10) + 10*(x-10) 

                          = x² - 10x  + 10x - 10²

                          = x² - 10²

Does this make it clearer?

If not, show how you got 2x^2.

Oh ok!Alan i just made a slight mistake!and so was getting a wrong answer!thanks for telling me!i'd give u a point for that!