Implicit Differentiation & Related Rates Quiz with Answers

Question 1

Find $\frac{dy}{dx}$ if $x^2+y^2=25$.

Accepted Answer

$\frac{dy}{dx}=-\frac{x}{y}$

Answer

$\frac{dy}{dx}=\frac{x}{y}$

Answer

$\frac{dy}{dx}=-\frac{2x}{2y\frac{dy}{dx}}$

Answer

$\frac{dy}{dx}=-\frac{y}{x}$

Question 2

A ladder of length $10$ ft leans against a wall. If the bottom slides away at $\frac{dx}{dt}=2$ ft/s when the bottom is $x=6$ ft from the wall, how fast is the top sliding down ($\frac{dy}{dt}$)? (Let $y$ be the height.)

Accepted Answer

$\frac{dy}{dt}=-\frac{3}{2}$ ft/s

Answer

$\frac{dy}{dt}=-\frac{2}{3}$ ft/s

Answer

$\frac{dy}{dt}=-\frac{5}{4}$ ft/s

Answer

$\frac{dy}{dt}=\frac{3}{2}$ ft/s

Question 3

Given $x^2y+\sin y=3$, find $\frac{d^2y}{dx^2}$ in terms of $x$ and $y$ (do not substitute a point).

Accepted Answer

$\displaystyle \frac{d^2y}{dx^2}=\frac{-2y-4x\frac{dy}{dx}+\sin(y)\left(\frac{dy}{dx}\right)^2}{x^2+\cos y}$

Answer

$\displaystyle \frac{d^2y}{dx^2}=\frac{-2y-2x\frac{dy}{dx}}{x^2+\cos y}$

Answer

$\displaystyle \frac{d^2y}{dx^2}=\frac{-2y-4x\frac{dy}{dx}-\sin(y)\left(\frac{dy}{dx}\right)^2}{x^2+\cos y}$

Answer

$\displaystyle \frac{d^2y}{dx^2}=\frac{2y+4x\frac{dy}{dx}-\sin(y)\left(\frac{dy}{dx}\right)^2}{x^2+\cos y}$

Implicit Differentiation & Related Rates Quiz with Answers

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