证明:若函数f(x)在[x0,x0+δ]上连续,在(x0,x0+δ)内可导,且(A为常数),则f(x)在x0处的右导数存在且等于A.
A.在(a,b)内连续
B.在(a,b)内可导
C.在(a,b)内连续且可导
D.在[a,b]上连续,在(a,b)内可导
证明:若f'x(x,y),f´y(x,y)和f"xy(x,y)在点P0(x0,y0)的邻域存在,且f"xy(x,y)在点P0(x0,y0)连续,则f"yz(x,y)在P0(x0,y0)也存在,且
f"xy(x0,y0)=f"yz(x0,y0)(比定理1的条件弱).