Differentiation Question 24

Question: $ x\sqrt{1+y}+y\sqrt{1+x}=0 $ , then $ \frac{dy}{dx}= $

[RPET 1989, 96]

Options:

A) $ 1+x $

B) $ {{(1+x)}^{-2}} $

C) $ -{{(1+x)}^{-1}} $

D) $ -{{(1+x)}^{-2}} $

Show Answer

Answer:

Correct Answer: D

Solution:

$ x\sqrt{1+y}+y\sqrt{1+x}=0 $

Therefore $ x^{2}(1+y)=y^{2}(1+x) $

Therefore $ {{( \frac{d^{2}s}{dt^{2}} )} _{t=1/2}}=-8 $

Therefore $ x+y+xy=0,{ \because x\ne y } $

Therefore $ \frac{dy}{dx}=\frac{-1}{{{(1+x)}^{2}}} $ .