Define:
d/dx(f(x)) = f'(x)

where f'(x) = gradient (or slope) of f(x) at x = x.

Prove that:
d/dx(x^2) = 2x

without using calculus.

Only solution I can think of for this involves a line drawn between the points on the graph at (x-n) and (x+n) and doing some pretty simple algebra to determine its gradient, and showing that it gives 2x even as n tends to zero. I'm not sure this qualifies as a solution though, so I'll not post anything here quite yet... Ummmmm...?

Posted by Nick Reed on 2002-07-31 22:38:33