题目内容：

利用导数的定义,求函数f(x)=2√x的导函数f'(x)

优质解答

dx 趋近于 0f(x)'=lim [2*(x+dx)^(1/2)-2*x^(1/2)]/dx=lim [2*(x+dx)^(1/2)-2*x^(1/2)][2*(x+dx)^(1/2)+2*x^(1/2)]/[2*(x+dx)^(1/2)+2*x^(1/2)]dx=lim 4dx/[2*(x+dx)^(1/2)+2*x^(1/2)]dx=lim 4/[2*(x+dx)^(1/2)+2*x^...