[微積] chain rule

[ytyt5239 (ytyt)]

1.Suppose y= is a curve that always lies above the x-axis and never has a
horizontal tangent,where f is differentiable everywhere.For what value of y is
the rate of change of y五次方 with respect to x eighty times the rate of change
of y with respect to x?   個人不太懂題目後半段的意思ˊˋ??不知怎解
2.(a)Write｜x｜= 開根號x的平方 and use the Chain Rule to show that d｜x｜/dx =
     x/｜x｜
     第二題不知前面的提示有何意義啊??

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推 cheesesteak :1. d(y^5)/dx=8 dy/dx
推 cheesesteak :2. d sqrt x^2 /dx=1/(2 sqrt x^2) *2x=x/|x|