(①)Prove Lagrange theorem:if the function f (x)in continuous on la,b],can guide inthe (a,b),there are some fE(a,b),makes the f(b)-f(a)=f'()(b a).(i)Prove:if f(x)is continuous at x 0,can guide within the (0,8),(8 >0)limf'(x)=A,the f(0),and f(0)=A.x-0+