切线的斜率,即是导数在该点处的取值~y=1/根号x=x^(-1/2),^表示乘方,x^(-1/2)表示x的-1/2次方y'=(-1/2)x^(-1/2-1)=(-1/2)x^(-3/2)所以,当x=9时该处切线的斜率k=y'=(-1/2)×9^(-3/2)=(-1/2)×(1/729)^(1/2)=(-1/2)×(1...