question_answer

If \[y={{(x+\sqrt{1+{{x}^{2}}})}^{n}},\] then \[(1+{{x}^{2}})\frac{{{d}^{2}}y}{d{{x}^{2}}}=x\frac{dy}{dx}\]  is

A)  \[{{n}^{2}}y\]           

B)  \[-{{n}^{2}}y\]

C)  \[-y\]                           

D)  \[2{{x}^{2}}y\]

E)  None of these