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MTH 102 MTH 102 Past Questions Objective Question

Question

Given that x³+x+y³+3y=6. Find dy/dx at (1,1)
Options
A -3/4
B -2/3
Correct Answer
C 5/2
D 2/3
Correct Answer

Option B is the correct answer.

Detailed Explanation

To find dy/dx, differentiate the given implicit equation x³+x+y³+3y=6 with respect to x:d/dx(x³) + d/dx(x) + d/dx(y³) + d/dx(3y) = d/dx(6)3x² + 1 + 3y²(dy/dx) + 3(dy/dx) = 0Now, group the terms containing dy/dx:(3y² + 3) dy/dx = -3x² - 1Solve for dy/dx:dy/dx = (-3x² - 1) / (3y² + 3)Finally, substitute the given point (x,y) = (1,1) into the expression for dy/dx:dy/dx = (-3(1)² - 1) / (3(1)² + 3)dy/dx = (-3 - 1) / (3 + 3)dy/dx = -4 / 6dy/dx = -2/3.This matches option B.

Hint

Apply implicit differentiation. Remember to use the chain rule when differentiating terms involving 'y' with respect to 'x' (e.g., d/dx(y³) = 3y² dy/dx). After finding the general expression for dy/dx, substitute the given coordinates.

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