Question

If 2x + 2y = 2x + y, then the value of $\frac{dy}{dx}$ at x = y = 1 is

• A. 0
• B. –1
• C. 1
• D. 2

Answer 1

Answer: (B)

–1

Answer 2

If y = tan$\left\lbrack \frac{1}{2} \times \tan^{- 1}U + \frac{1}{2} \times 2\tan^{- 1}U \right\rbrack$

= tan(2 tan^–1 U) = tan$\left\lbrack \tan^{- 1}\frac{2U}{1 - U^{2}} \right\rbrack$

So y = $\frac{2U}{1 - U^{2}}$ = x than $\frac{dy}{dx}$ = 1