Engineering Board Exam Reviewer · Implicit Differentiation · hard

Find d2y/dx2 if x2+y2=4.

1. 4y3
2. - 4y2
3. - 4y3
4. - xy3

Answer

C. - 4y3

Solution

First, y'=- xy. Then y''=-y-xy'/y2=-y+x2/y/y2=-y2+x2/y3=-4/y3.

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