f'(x)=x'(x–1)(x–2)...(x–99)+x(x–1)'(x–2)...(x–99)+x(x–1)(x–2)'...(x–99)+...+x(x–1)(x–2)...(x–99)'。
当x=0时;x(x–1)'(x–2)...(x–99)+x(x–1)(x–2)'...(x–99)+...+x(x–1)(x–2)...(x–99)' =0;
因为0乘任何数等于0。
所以f'(0)=(-1)*(-2)*...*(-99)=-99!。是负99的阶乘哦。。
0!!!!!!!!!!!!!!!!!