Find the first principle the derivative of 2x(2)-x with respect to x
let f(x) = 2x^2 - x
f(x+h) = 2(x+h)^2 - (x+h)
= 2x^2 + 4xh + 2h^2 - x - h
f ' (x) = lim[( (2x^2 + 4xh + 2h^2 - x - h) - (2x^2 - x) )/h ] as h ---> 0
= lim ( (4xh + 2h^2 - h)/h ) as h ---> 0
= lim 4x + 2h - 1 , as h ---> 0
= 4x - 1