f(x) = x/(3x + 1), prove f(x) is differentiable at point 2. Ok so I've had several attempts at this.... Using Q(h) = (f(h) - f(2))/h I eventually end up with (h^2 -2h)/(7(3h + 1)) Obviously the above is rubbish because it I differentiate f(x) using the normal rules then dy/dx = 1/(3x + 1)^2 What am I missing here? Also I've tried using the difference quotient to prove it is differentiable but same result - just rubbish. f(c + h) - f(c)/ h The above also doesn't work out either! Please hep!!