Question Detail

MTH 102 MTH 102 Past Questions Objective Question

Question

Given that \(x^3 + x + y^3 + 3y = 6\), find \(\frac{dy}{dx}\) at \((1, 1)\).
Options
A \(-\frac{3}{4}\)
B \(-\frac{2}{3}\)
C \(-\frac{5}{2}\)
D \(-\frac{2}{3}\)
Correct Answer
Correct Answer

Option D is the correct answer.

Detailed Explanation

We use implicit differentiation with respect to (x):(\frac{d}{dx}(x^3) + \frac{d}{dx}(x) + \frac{d}{dx}(y^3) + \frac{d}{dx}(3y) = \frac{d}{dx}(6))(3x^2 + 1 + 3y^2\frac{dy}{dx} + 3\frac{dy}{dx} = 0)Factor out (\frac{dy}{dx}):((3y^2 + 3)\frac{dy}{dx} = -(3x^2 + 1))(\frac{dy}{dx} = -\frac{3x^2 + 1}{3y^2 + 3})Now, substitute the point ((x, y) = (1, 1)):(\frac{dy}{dx} = -\frac{3(1)^2 + 1}{3(1)^2 + 3})(= -\frac{3 + 1}{3 + 3})(= -\frac{4}{6})(= -\frac{2}{3}).

Hint

Differentiate implicitly with respect to \(x\), remembering to use the chain rule for terms involving \(y\).

Question Info