Let f (x) = x (x + 1) (x + 2) (x + n), then f ′ (0)=______ .

Let f (x) = x (x + 1) (x + 2) (x + n), then f ′ (0)=______ .

∵f′(0)=limx→0f(x)−f(0)x=limx→0x(x+1)… (x+n)xlimx→0(x+1)… (x+n)=n!