AP Calculus AB Fun 3 D Calculate Derivatives of Implicitly Defined Functions Questions question 1 [Maximum number: 2]
Consider the curve G defined by the equation y 3 − y 2 − y + 1 4 x 2 = 0 y^{3}-y^{2}-y+\frac{1}{4} x^{2}=0 y 3 − y 2 − y + 4 1 x 2 = 0 .
Show that d y d x = − x 2 ( 3 y 2 − 2 y − 1 ) \frac{d y}{d x}=\frac{-x}{2\left(3 y^{2}-2 y-1\right)} d x d y = 2 ( 3 y 2 − 2 y − 1 ) − x .
d d x ( y 3 − y 2 − y + 1 4 x 2 ) = 0 ⇒ 3 y 2 d y d x − 2 y d y d x − d y d x + x 2 = 0 \begin{aligned} & \frac{d}{d x}\left(y^{3}-y^{2}-y+\frac{1}{4} x^{2}\right)=0 \\ & \Rightarrow 3 y^{2} \frac{d y}{d x}-2 y \frac{d y}{d x}-\frac{d y}{d x}+\frac{x}{2}=0 \end{aligned} d x d ( y 3 − y 2 − y + 4 1 x 2 ) = 0 ⇒ 3 y 2 d x d y − 2 y d x d y − d x d y + 2 x = 0 Implicit differentiation Point 1 (P1) ⇒ ( 3 y 2 − 2 y − 1 ) d y d x = − x 2 ⇒ d y d x = − x 2 ( 3 y 2 − 2 y − 1 ) \begin{aligned} & \Rightarrow\left(3 y^{2}-2 y-1\right) \frac{d y}{d x}=-\frac{x}{2} \\ & \Rightarrow \frac{d y}{d x}=\frac{-x}{2\left(3 y^{2}-2 y-1\right)} \end{aligned} ⇒ ( 3 y 2 − 2 y − 1 ) d x d y = − 2 x ⇒ d x d y = 2 ( 3 y 2 − 2 y − 1 ) − x Verification Point 2 (P2) Scoring Notes for Part A - P1 is earned only for the correct implicit differentiation of y 3 − y 2 − y + 1 4 x 2 = 0 y^{3}-y^{2}-y+\frac{1}{4}x^{2}=0 y 3 − y 2 − y + 4 1 x 2 = 0 . Alternative notation such as y ′ y^{\prime} y ′ is acceptable. - It is sufficient to present ( 3 y 2 − 2 y − 1 ) d y d x = − x 2 \left(3 y^{2}-2 y-1\right)\frac{d y}{d x}=-\frac{x}{2} ( 3 y 2 − 2 y − 1 ) d x d y = − 2 x to earn P2, provided there are no subsequent errors.
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