Question

Let xy=5 and let dy/dt=4. What is dx/dt when x=3 ?

Answer 1

`-36/5`

Explanation:

Differentiate xy=5, w.r.t

`x dy/dt + y dx/dt =0`

Now, given x=3, y would be `5/3`. Substituting these values `dy/dt=4` in the expression above,

`3 (4) +5/3 dx/dt=0`

This would give `dx/dt= -12 (3/5) = -36/5`

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