不要展开,直接用求导公式(uvw)'=u'vw+uv'w+uvw'就可以:
y=(x-1)²(x-3)³(x-4)⁴
y'=2(x-1)(x-3)³(x-4)⁴+3(x-1)²(x-3)²(x-4)⁴+4(x-1)²(x-3)³(x-4)³
=y[2/(x-1)+3/(x-3)+4/(x-4)]
y''=y'(2/(x-1)+3/(x-3)+4/(x-4)-y·[-2/(x-1)²+3/(x-3)²+4/(x-4)²]
两边求对数,然后对数的高阶可以变成系数,说到这可以了吧