Question

If log (x + y) –2xy = 0 . Then y′ (0) =

• A. 1
• B. –1
• C. 2
• D. 0

Answer 1

Answer: (A)

1

Answer 2

f(x, y) = log (x + y) –2xy = 0

$\frac{dy}{dx}$= – $\frac{\partial f/\partial x}{\partial f/\partial y}$= – $\frac{\left( \frac{1}{x + y} \right) - 2y}{\left( \frac{1}{x + y} \right) - 2x}$= – $\left( \frac{1 - 2}{1 - 0} \right)$= 1