求f(1-x)/((9-x的平方)的开方)的导函数

题目有点问题 是不是求f(X)=(1-x)/((9-x^2)的开方)的导函数?
如果是那么两边平方
f^2(X)=(1-x)^2/(9-x^2)
再两边求导
2f(X)f'(X)={ [(1-x)^2]'(9-x^2)-(9-x^2)'(1-x) }/[(9-x^2) ]^2
简化
f(X)f'(X)=(1-x)(X-9)/[(9-x^2) ]^2
f'(X)={ (1-x)(X-9)/[(9-x^2)]^2 }/{ (1-x)/((9-x^2)的开方) }
f'(X)=(X-9)/(9-x^2) ^1.5

也可以直接求导
f'(X)=[(1-x)'((9-x^2)的开方)-(1-x)((9-x^2)的开方)' ]/((9-x^2)的开方)^2
=[ -((9-x^2)的开方)-(1-x)(0.5(9-x^2)^-0.5)(-2X) ]/(9-x^2)
=[ -(9-x^2)-0.5(1-x)(-2X) ]/(9-x^2)^1.5
=(-9+x^2+X-X^2)/(9-x^2)^1.5
=(X-9)/(9-x^2)^1.5