1.

If \( 2^{x}+2^{y}=2^{x+y} \), then \( \frac{d y}{d x} \) is equal to \( \frac{2^{x}+2^{y}}{2^{x}-2^{y}} \) \( \frac{2^{x}+2^{y}}{1+2^{x+y}} \) \( 2^{x-y}\left[\frac{2^{y}-1}{1-2^{x}}\right] \) \( \frac{2^{x+y}-2^{x}}{2^{y}} \)

Answer»

We have 2x + 2y = 2x + y

By differentiating both sides w.r.to x, we get

2ln2 + 2ln2 \(\frac{dy}{dx}=\) 2x+y (1 + \(\frac{dy}{dx}\)) ln2

(\(\because\) \(\frac{d}{dx}a^x=a^x \) ln a)

⇒ ln 2 (2x + 2y\(\frac{dy}{dx}\)) = 2x+y + 2x+y \(\frac{dy}{dx}\)

⇒ (2x+y - 2y)\(\frac{dy}{dx}\) = 2x - 2x+y

⇒ 2y(2x - 1) \(\frac{dy}{dx}\) = 2x(1 - 2y)

⇒ \(\frac{dy}{dx}\) = \(\frac{2^x(1-2^y)}{2^y(2^x-1)}\) = \(\frac{2^{x-y}(1-2^y)}{2^x-1}\)

 = \(\frac{2^{x-y}(2^y-1)}{1-2^x}\)



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