Precalculus Examples

$x^{2} y - x y^{2} + x^{2} + y^{2} = 0$

Step 1

Differentiate both sides of the equation.

$\frac{d}{d y} (x^{2} y - x y^{2} + x^{2} + y^{2}) = \frac{d}{d y} (0)$

Step 2

Differentiate the left side of the equation.

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Step 2.1

By the Sum Rule, the derivative of $x^{2} y - x y^{2} + x^{2} + y^{2}$ with respect to $y$ is $\frac{d}{d y} [x^{2} y] + \frac{d}{d y} [- x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$ .

$\frac{d}{d y} [x^{2} y] + \frac{d}{d y} [- x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.2

Evaluate $\frac{d}{d y} [x^{2} y]$ .

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Step 2.2.1

Differentiate using the Product Rule which states that $\frac{d}{d y} [f (y) g (y)]$ is $f (y) \frac{d}{d y} [g (y)] + g (y) \frac{d}{d y} [f (y)]$ where $f (y) = x^{2}$ and $g (y) = y$ .

$x^{2} \frac{d}{d y} [y] + y \frac{d}{d y} [x^{2}] + \frac{d}{d y} [- x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.2.2

Differentiate using the Power Rule which states that $\frac{d}{d y} [y^{n}]$ is $n y^{n - 1}$ where $n = 1$ .

$x^{2} \cdot 1 + y \frac{d}{d y} [x^{2}] + \frac{d}{d y} [- x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.2.3

Differentiate using the chain rule, which states that $\frac{d}{d y} [f (g (y))]$ is $f' (g (y)) g' (y)$ where $f (y) = y^{2}$ and $g (y) = x$ .

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Step 2.2.3.1

To apply the Chain Rule, set $u_{1}$ as $x$ .

$x^{2} \cdot 1 + y (\frac{d}{d u_{1}} [{u_{1}}^{2}] \frac{d}{d y} [x]) + \frac{d}{d y} [- x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.2.3.2

Differentiate using the Power Rule which states that $\frac{d}{d u_{1}} [{u_{1}}^{n}]$ is $n {u_{1}}^{n - 1}$ where $n = 2$ .

$x^{2} \cdot 1 + y (2 u_{1} \frac{d}{d y} [x]) + \frac{d}{d y} [- x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.2.3.3

Replace all occurrences of $u_{1}$ with $x$ .

$x^{2} \cdot 1 + y (2 x \frac{d}{d y} [x]) + \frac{d}{d y} [- x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.2.4

Rewrite $\frac{d}{d y} [x]$ as $x'$ .

$x^{2} \cdot 1 + y (2 x x') + \frac{d}{d y} [- x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.2.5

Multiply $x^{2}$ by $1$ .

$x^{2} + y (2 x x') + \frac{d}{d y} [- x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.2.6

Move $2$ to the left of $y$ .

$x^{2} + 2 y x x' + \frac{d}{d y} [- x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.3

Evaluate $\frac{d}{d y} [- x y^{2}]$ .

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Step 2.3.1

Since $- 1$ is constant with respect to $y$ , the derivative of $- x y^{2}$ with respect to $y$ is $- \frac{d}{d y} [x y^{2}]$ .

$x^{2} + 2 y x x' - \frac{d}{d y} [x y^{2}] + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.3.2

Differentiate using the Product Rule which states that $\frac{d}{d y} [f (y) g (y)]$ is $f (y) \frac{d}{d y} [g (y)] + g (y) \frac{d}{d y} [f (y)]$ where $f (y) = x$ and $g (y) = y^{2}$ .

$x^{2} + 2 y x x' - (x \frac{d}{d y} [y^{2}] + y^{2} \frac{d}{d y} [x]) + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.3.3

Differentiate using the Power Rule which states that $\frac{d}{d y} [y^{n}]$ is $n y^{n - 1}$ where $n = 2$ .

$x^{2} + 2 y x x' - (x (2 y) + y^{2} \frac{d}{d y} [x]) + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.3.4

Rewrite $\frac{d}{d y} [x]$ as $x'$ .

$x^{2} + 2 y x x' - (x (2 y) + y^{2} x') + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.3.5

Move $2$ to the left of $x$ .

$x^{2} + 2 y x x' - (2 x y + y^{2} x') + \frac{d}{d y} [x^{2}] + \frac{d}{d y} [y^{2}]$

Step 2.4

Evaluate $\frac{d}{d y} [x^{2}]$ .

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Step 2.4.1

Differentiate using the chain rule, which states that $\frac{d}{d y} [f (g (y))]$ is $f' (g (y)) g' (y)$ where $f (y) = y^{2}$ and $g (y) = x$ .

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Step 2.4.1.1

To apply the Chain Rule, set $u_{2}$ as $x$ .

$x^{2} + 2 y x x' - (2 x y + y^{2} x') + \frac{d}{d u_{2}} [{u_{2}}^{2}] \frac{d}{d y} [x] + \frac{d}{d y} [y^{2}]$

Step 2.4.1.2

Differentiate using the Power Rule which states that $\frac{d}{d u_{2}} [{u_{2}}^{n}]$ is $n {u_{2}}^{n - 1}$ where $n = 2$ .

$x^{2} + 2 y x x' - (2 x y + y^{2} x') + 2 u_{2} \frac{d}{d y} [x] + \frac{d}{d y} [y^{2}]$

Step 2.4.1.3

Replace all occurrences of $u_{2}$ with $x$ .

$x^{2} + 2 y x x' - (2 x y + y^{2} x') + 2 x \frac{d}{d y} [x] + \frac{d}{d y} [y^{2}]$

Step 2.4.2

Rewrite $\frac{d}{d y} [x]$ as $x'$ .

$x^{2} + 2 y x x' - (2 x y + y^{2} x') + 2 x x' + \frac{d}{d y} [y^{2}]$

Step 2.5

Differentiate using the Power Rule which states that $\frac{d}{d y} [y^{n}]$ is $n y^{n - 1}$ where $n = 2$ .

$x^{2} + 2 y x x' - (2 x y + y^{2} x') + 2 x x' + 2 y$

Step 2.6

Simplify.

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Step 2.6.1

Apply the distributive property.

$x^{2} + 2 y x x' - (2 x y) - (y^{2} x') + 2 x x' + 2 y$

Step 2.6.2

Multiply $2$ by $- 1$ .

$x^{2} + 2 y x x' - 2 x y - y^{2} x' + 2 x x' + 2 y$

Step 2.6.3

Reorder terms.

$x^{2} + 2 x y x' - 2 x y - y^{2} x' + 2 x x' + 2 y$

Step 3

Since $0$ is constant with respect to $y$ , the derivative of $0$ with respect to $y$ is $0$ .

$0$

Step 4

Reform the equation by setting the left side equal to the right side.

$x^{2} + 2 x y x' - 2 x y - y^{2} x' + 2 x x' + 2 y = 0$

Step 5

Solve for $x'$ .

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Step 5.1

Move all terms not containing $x'$ to the right side of the equation.

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Step 5.1.1

Subtract $x^{2}$ from both sides of the equation.

$2 x y x' - 2 x y - y^{2} x' + 2 x x' + 2 y = - x^{2}$

Step 5.1.2

Add $2 x y$ to both sides of the equation.

$2 x y x' - y^{2} x' + 2 x x' + 2 y = - x^{2} + 2 x y$

Step 5.1.3

Subtract $2 y$ from both sides of the equation.

$2 x y x' - y^{2} x' + 2 x x' = - x^{2} + 2 x y - 2 y$

Step 5.2

Factor $x'$ out of $2 x y x' - y^{2} x' + 2 x x'$ .

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Step 5.2.1

Factor $x'$ out of $2 x y x'$ .

$x' (2 x y) - y^{2} x' + 2 x x' = - x^{2} + 2 x y - 2 y$

Step 5.2.2

Factor $x'$ out of $- y^{2} x'$ .

$x' (2 x y) + x' (- y^{2}) + 2 x x' = - x^{2} + 2 x y - 2 y$

Step 5.2.3

Factor $x'$ out of $2 x x'$ .

$x' (2 x y) + x' (- y^{2}) + x' (2 x) = - x^{2} + 2 x y - 2 y$

Step 5.2.4

Factor $x'$ out of $x' (2 x y) + x' (- y^{2})$ .

$x' (2 x y - y^{2}) + x' (2 x) = - x^{2} + 2 x y - 2 y$

Step 5.2.5

Factor $x'$ out of $x' (2 x y - y^{2}) + x' (2 x)$ .

$x' (2 x y - y^{2} + 2 x) = - x^{2} + 2 x y - 2 y$

Step 5.3

Divide each term in $x' (2 x y - y^{2} + 2 x) = - x^{2} + 2 x y - 2 y$ by $2 x y - y^{2} + 2 x$ and simplify.

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Step 5.3.1

Divide each term in $x' (2 x y - y^{2} + 2 x) = - x^{2} + 2 x y - 2 y$ by $2 x y - y^{2} + 2 x$ .

$\frac{x' (2 x y - y^{2} + 2 x)}{2 x y - y^{2} + 2 x} = \frac{- x^{2}}{2 x y - y^{2} + 2 x} + \frac{2 x y}{2 x y - y^{2} + 2 x} + \frac{- 2 y}{2 x y - y^{2} + 2 x}$

Step 5.3.2

Simplify the left side.

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Step 5.3.2.1

Cancel the common factor of $2 x y - y^{2} + 2 x$ .

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Step 5.3.2.1.1

Cancel the common factor.

$\frac{x' (2 x y - y^{2} + 2 x)}{2 x y - y^{2} + 2 x} = \frac{- x^{2}}{2 x y - y^{2} + 2 x} + \frac{2 x y}{2 x y - y^{2} + 2 x} + \frac{- 2 y}{2 x y - y^{2} + 2 x}$

Step 5.3.2.1.2

Divide $x'$ by $1$ .

$x' = \frac{- x^{2}}{2 x y - y^{2} + 2 x} + \frac{2 x y}{2 x y - y^{2} + 2 x} + \frac{- 2 y}{2 x y - y^{2} + 2 x}$

Step 5.3.3

Simplify the right side.

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Step 5.3.3.1

Simplify each term.

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Step 5.3.3.1.1

Move the negative in front of the fraction.

$x' = - \frac{x^{2}}{2 x y - y^{2} + 2 x} + \frac{2 x y}{2 x y - y^{2} + 2 x} + \frac{- 2 y}{2 x y - y^{2} + 2 x}$

Step 5.3.3.1.2

Move the negative in front of the fraction.

$x' = - \frac{x^{2}}{2 x y - y^{2} + 2 x} + \frac{2 x y}{2 x y - y^{2} + 2 x} - \frac{2 y}{2 x y - y^{2} + 2 x}$

Step 5.3.3.2

Simplify terms.

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Step 5.3.3.2.1

Combine the numerators over the common denominator.

$x' = \frac{- x^{2} + 2 x y}{2 x y - y^{2} + 2 x} - \frac{2 y}{2 x y - y^{2} + 2 x}$

Step 5.3.3.2.2

Combine the numerators over the common denominator.

$x' = \frac{- x^{2} + 2 x y - 2 y}{2 x y - y^{2} + 2 x}$

Step 5.3.3.2.3

Factor $- 1$ out of $- x^{2}$ .

$x' = \frac{- (x^{2}) + 2 x y - 2 y}{2 x y - y^{2} + 2 x}$

Step 5.3.3.2.4

Factor $- 1$ out of $2 x y$ .

$x' = \frac{- (x^{2}) - (- 2 x y) - 2 y}{2 x y - y^{2} + 2 x}$

Step 5.3.3.2.5

Factor $- 1$ out of $- (x^{2}) - (- 2 x y)$ .

$x' = \frac{- (x^{2} - 2 x y) - 2 y}{2 x y - y^{2} + 2 x}$

Step 5.3.3.2.6

Factor $- 1$ out of $- 2 y$ .

$x' = \frac{- (x^{2} - 2 x y) - (2 y)}{2 x y - y^{2} + 2 x}$

Step 5.3.3.2.7

Factor $- 1$ out of $- (x^{2} - 2 x y) - (2 y)$ .

$x' = \frac{- (x^{2} - 2 x y + 2 y)}{2 x y - y^{2} + 2 x}$

Step 5.3.3.2.8

Simplify the expression.

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Step 5.3.3.2.8.1

Rewrite $- (x^{2} - 2 x y + 2 y)$ as $- 1 (x^{2} - 2 x y + 2 y)$ .

$x' = \frac{- 1 (x^{2} - 2 x y + 2 y)}{2 x y - y^{2} + 2 x}$

Step 5.3.3.2.8.2

Move the negative in front of the fraction.

$x' = - \frac{x^{2} - 2 x y + 2 y}{2 x y - y^{2} + 2 x}$

Step 6

Replace $x'$ with $\frac{d x}{d y}$ .

$\frac{d x}{d y} = - \frac{x^{2} - 2 x y + 2 y}{2 x y - y^{2} + 2 x}$