隐函数求导x^(1/2)+y^(1/2)=9,求在点（1,64）切线的斜率,

[x^(1/2)+y^(1/2)]'=0,1/[2(x^(1/2)]+y'/[2(y^(1/2))]=0,y'=-(y/x)^(1/2),y'(1)=-64^(1/2)=-8.
切线方程为：y-64=-8(x-1),8x+y-72=0.