Implicit differentiation dy/dx

freetofu
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Homework Statement


Determine dy/dx
xy^-2 = 1

Homework Equations




The Attempt at a Solution


Here's what I tried:
y^-2 - 2xy^-3(dy/dx) = 1
dy/dx = (y - y^3)/2x

The answer in the book is y/2x. How do you do it?
 
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You differentiated the left side but not the right side

d/dx(1) = ?
 
Thanks. Duh.
 
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