ln|5x-7y| 求导
问题描述:
ln|5x-7y| 求导
答
这是二元函数,应该是求偏导数:记
f(x,y) = ln|5x-7y|,
则
Df(x,y)/Dx = 5/(5x-7y),
Df(x,y)/Dy = -7/(5x-7y).