Calculus Examples

$\frac{d y}{d x} + 4 y = 3 \cos (2 x)$

Step 1

The integrating factor is defined by the formula $e^{\int P (x) d x}$ , where $P (x) = 4$ .

Tap for more steps...

Step 1.1

Set up the integration.

$e^{\int 4 d x}$

Step 1.2

Apply the constant rule.

$e^{4 x + C}$

Step 1.3

Remove the constant of integration.

$e^{4 x}$

Step 2

Multiply each term by the integrating factor $e^{4 x}$ .

Tap for more steps...

Step 2.1

Multiply each term by $e^{4 x}$ .

$e^{4 x} \frac{d y}{d x} + e^{4 x} (4 y) = e^{4 x} (3 \cos (2 x))$

Step 2.2

Rewrite using the commutative property of multiplication.

$e^{4 x} \frac{d y}{d x} + 4 e^{4 x} y = e^{4 x} (3 \cos (2 x))$

Step 2.3

Rewrite using the commutative property of multiplication.

$e^{4 x} \frac{d y}{d x} + 4 e^{4 x} y = 3 e^{4 x} \cos (2 x)$

Step 2.4

Reorder factors in $e^{4 x} \frac{d y}{d x} + 4 e^{4 x} y = 3 e^{4 x} \cos (2 x)$ .

$e^{4 x} \frac{d y}{d x} + 4 y e^{4 x} = 3 e^{4 x} \cos (2 x)$

Step 3

Rewrite the left side as a result of differentiating a product.

$\frac{d}{d x} [e^{4 x} y] = 3 e^{4 x} \cos (2 x)$

Step 4

Set up an integral on each side.

$\int \frac{d}{d x} [e^{4 x} y] d x = \int 3 e^{4 x} \cos (2 x) d x$

Step 5

Integrate the left side.

$e^{4 x} y = \int 3 e^{4 x} \cos (2 x) d x$

Step 6

Integrate the right side.

Tap for more steps...

Step 6.1

Since $3$ is constant with respect to $x$ , move $3$ out of the integral.

$e^{4 x} y = 3 \int e^{4 x} \cos (2 x) d x$

Step 6.2

Reorder $e^{4 x}$ and $\cos (2 x)$ .

$e^{4 x} y = 3 \int \cos (2 x) e^{4 x} d x$

Step 6.3

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = \cos (2 x)$ and $d v = e^{4 x}$ .

$e^{4 x} y = 3 (\cos (2 x) (\frac{1}{4} e^{4 x}) - \int \frac{1}{4} e^{4 x} (- 2 \sin (2 x)) d x)$

Step 6.4

Since $\frac{1}{4} \cdot - 2$ is constant with respect to $x$ , move $\frac{1}{4} \cdot - 2$ out of the integral.

$e^{4 x} y = 3 (\cos (2 x) (\frac{1}{4} e^{4 x}) - (\frac{1}{4} \cdot - 2 \int e^{4 x} (\sin (2 x)) d x))$

Step 6.5

Combine fractions.

Tap for more steps...

Step 6.5.1

Combine $\frac{1}{4}$ and $e^{4 x}$ .

$e^{4 x} y = 3 (\cos (2 x) \frac{e^{4 x}}{4} - (\frac{1}{4} \cdot - 2 \int e^{4 x} (\sin (2 x)) d x))$

Step 6.5.2

Combine $\cos (2 x)$ and $\frac{e^{4 x}}{4}$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - (\frac{1}{4} \cdot - 2 \int e^{4 x} (\sin (2 x)) d x))$

Step 6.5.3

Combine $\frac{1}{4}$ and $- 2$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - (\frac{- 2}{4} \int e^{4 x} (\sin (2 x)) d x))$

Step 6.5.4

Reorder $e^{4 x}$ and $\sin (2 x)$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - (\frac{- 2}{4} \int \sin (2 x) e^{4 x} d x))$

Step 6.6

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = \sin (2 x)$ and $d v = e^{4 x}$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - (\frac{- 2}{4} (\sin (2 x) (\frac{1}{4} e^{4 x}) - \int \frac{1}{4} e^{4 x} (2 \cos (2 x)) d x)))$

Step 6.7

Since $\frac{1}{4} \cdot 2$ is constant with respect to $x$ , move $\frac{1}{4} \cdot 2$ out of the integral.

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - (\frac{- 2}{4} (\sin (2 x) (\frac{1}{4} e^{4 x}) - (\frac{1}{4} \cdot 2 \int e^{4 x} (\cos (2 x)) d x))))$

Step 6.8

Simplify terms.

Tap for more steps...

Step 6.8.1

Combine $\frac{1}{4}$ and $e^{4 x}$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - (\frac{- 2}{4} (\sin (2 x) \frac{e^{4 x}}{4} - (\frac{1}{4} \cdot 2 \int e^{4 x} (\cos (2 x)) d x))))$

Step 6.8.2

Combine $\sin (2 x)$ and $\frac{e^{4 x}}{4}$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - (\frac{- 2}{4} (\frac{\sin (2 x) e^{4 x}}{4} - (\frac{1}{4} \cdot 2 \int e^{4 x} (\cos (2 x)) d x))))$

Step 6.8.3

Combine $\frac{1}{4}$ and $2$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - (\frac{- 2}{4} (\frac{\sin (2 x) e^{4 x}}{4} - (\frac{2}{4} \int e^{4 x} (\cos (2 x)) d x))))$

Step 6.8.4

Apply the distributive property.

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - \frac{- 2}{4} \cdot \frac{\sin (2 x) e^{4 x}}{4} - \frac{- 2}{4} (- (\frac{2}{4} \int e^{4 x} (\cos (2 x)) d x)))$

Step 6.8.5

Multiply $\frac{\sin (2 x) e^{4 x}}{4}$ by $\frac{- 2}{4}$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - \frac{\sin (2 x) e^{4 x} \cdot - 2}{4 \cdot 4} - \frac{- 2}{4} (- (\frac{2}{4} \int e^{4 x} (\cos (2 x)) d x)))$

Step 6.8.6

Multiply.

Tap for more steps...

Step 6.8.6.1

Multiply $4$ by $4$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - \frac{\sin (2 x) e^{4 x} \cdot - 2}{16} - \frac{- 2}{4} (- (\frac{2}{4} \int e^{4 x} (\cos (2 x)) d x)))$

Step 6.8.6.2

Multiply $- 1$ by $- 1$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - \frac{\sin (2 x) e^{4 x} \cdot - 2}{16} + 1 (\frac{- 2}{4}) (\frac{2}{4} \int e^{4 x} (\cos (2 x)) d x))$

Step 6.8.6.3

Multiply $\frac{- 2}{4}$ by $1$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - \frac{\sin (2 x) e^{4 x} \cdot - 2}{16} + \frac{- 2}{4} (\frac{2}{4} \int e^{4 x} (\cos (2 x)) d x))$

Step 6.8.7

Multiply $\frac{2}{4}$ by $\frac{- 2}{4}$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - \frac{\sin (2 x) e^{4 x} \cdot - 2}{16} + \frac{2 \cdot - 2}{4 \cdot 4} \int e^{4 x} (\cos (2 x)) d x)$

Step 6.8.8

Multiply.

Tap for more steps...

Step 6.8.8.1

Multiply $2$ by $- 2$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - \frac{\sin (2 x) e^{4 x} \cdot - 2}{16} + \frac{- 4}{4 \cdot 4} \int e^{4 x} (\cos (2 x)) d x)$

Step 6.8.8.2

Multiply $4$ by $4$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{4} - \frac{\sin (2 x) e^{4 x} \cdot - 2}{16} + \frac{- 4}{16} \int e^{4 x} (\cos (2 x)) d x)$

Step 6.9

Solving for $\int e^{4 x} \cos (2 x) d x$ , we find that $\int e^{4 x} \cos (2 x) d x$ = $\frac{\frac{\cos (2 x) e^{4 x}}{4} - \frac{\sin (2 x) e^{4 x} \cdot - 2}{16}}{\frac{20}{16}}$ .

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} - \frac{\sin (2 x) e^{4 x} \cdot - 2}{16}}{\frac{20}{16}} + C)$

Step 6.10

Simplify the answer.

Tap for more steps...

Step 6.10.1

Simplify.

Tap for more steps...

Step 6.10.1.1

Move $- 2$ to the left of $\sin (2 x) e^{4 x}$ .

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} - \frac{- 2 \cdot (\sin (2 x) e^{4 x})}{16}}{\frac{20}{16}} + C)$

Step 6.10.1.2

Cancel the common factor of $- 2$ and $16$ .

Tap for more steps...

Step 6.10.1.2.1

Factor $2$ out of $- 2 \sin (2 x) e^{4 x}$ .

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} - \frac{2 (- \sin (2 x) e^{4 x})}{16}}{\frac{20}{16}} + C)$

Step 6.10.1.2.2

Cancel the common factors.

Tap for more steps...

Step 6.10.1.2.2.1

Factor $2$ out of $16$ .

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} - \frac{2 (- \sin (2 x) e^{4 x})}{2 (8)}}{\frac{20}{16}} + C)$

Step 6.10.1.2.2.2

Cancel the common factor.

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} - \frac{2 (- \sin (2 x) e^{4 x})}{2 \cdot 8}}{\frac{20}{16}} + C)$

Step 6.10.1.2.2.3

Rewrite the expression.

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} - \frac{- \sin (2 x) e^{4 x}}{8}}{\frac{20}{16}} + C)$

Step 6.10.1.3

Move the negative in front of the fraction.

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} - - \frac{\sin (2 x) e^{4 x}}{8}}{\frac{20}{16}} + C)$

Step 6.10.1.4

Multiply $- 1$ by $- 1$ .

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} + 1 \frac{\sin (2 x) e^{4 x}}{8}}{\frac{20}{16}} + C)$

Step 6.10.1.5

Multiply $\frac{\sin (2 x) e^{4 x}}{8}$ by $1$ .

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} + \frac{\sin (2 x) e^{4 x}}{8}}{\frac{20}{16}} + C)$

Step 6.10.1.6

Cancel the common factor of $20$ and $16$ .

Tap for more steps...

Step 6.10.1.6.1

Factor $4$ out of $20$ .

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} + \frac{\sin (2 x) e^{4 x}}{8}}{\frac{4 (5)}{16}} + C)$

Step 6.10.1.6.2

Cancel the common factors.

Tap for more steps...

Step 6.10.1.6.2.1

Factor $4$ out of $16$ .

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} + \frac{\sin (2 x) e^{4 x}}{8}}{\frac{4 \cdot 5}{4 \cdot 4}} + C)$

Step 6.10.1.6.2.2

Cancel the common factor.

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} + \frac{\sin (2 x) e^{4 x}}{8}}{\frac{4 \cdot 5}{4 \cdot 4}} + C)$

Step 6.10.1.6.2.3

Rewrite the expression.

$e^{4 x} y = 3 (\frac{\frac{\cos (2 x) e^{4 x}}{4} + \frac{\sin (2 x) e^{4 x}}{8}}{\frac{5}{4}} + C)$

Step 6.10.1.7

Multiply by the reciprocal of the fraction to divide by $\frac{5}{4}$ .

$e^{4 x} y = 3 ((\frac{\cos (2 x) e^{4 x}}{4} + \frac{\sin (2 x) e^{4 x}}{8}) \frac{4}{5} + C)$

Step 6.10.2

Rewrite $3 ((\frac{\cos (2 x) e^{4 x}}{4} + \frac{\sin (2 x) e^{4 x}}{8}) \frac{4}{5} + C)$ as $3 (\frac{\cos (2 x) e^{4 x} \cdot 4}{4 \cdot 5} + \frac{\sin (2 x) e^{4 x} \cdot 4}{8 \cdot 5}) + C$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x} \cdot 4}{4 \cdot 5} + \frac{\sin (2 x) e^{4 x} \cdot 4}{8 \cdot 5}) + C$

Step 6.10.3

Simplify.

Tap for more steps...

Step 6.10.3.1

Move $4$ to the left of $\cos (2 x) e^{4 x}$ .

$e^{4 x} y = 3 (\frac{4 \cdot (\cos (2 x) e^{4 x})}{4 \cdot 5} + \frac{\sin (2 x) e^{4 x} \cdot 4}{8 \cdot 5}) + C$

Step 6.10.3.2

Multiply $4$ by $5$ .

$e^{4 x} y = 3 (\frac{4 \cos (2 x) e^{4 x}}{20} + \frac{\sin (2 x) e^{4 x} \cdot 4}{8 \cdot 5}) + C$

Step 6.10.3.3

Cancel the common factor of $4$ and $20$ .

Tap for more steps...

Step 6.10.3.3.1

Factor $4$ out of $4 \cos (2 x) e^{4 x}$ .

$e^{4 x} y = 3 (\frac{4 (\cos (2 x) e^{4 x})}{20} + \frac{\sin (2 x) e^{4 x} \cdot 4}{8 \cdot 5}) + C$

Step 6.10.3.3.2

Cancel the common factors.

Tap for more steps...

Step 6.10.3.3.2.1

Factor $4$ out of $20$ .

$e^{4 x} y = 3 (\frac{4 (\cos (2 x) e^{4 x})}{4 \cdot 5} + \frac{\sin (2 x) e^{4 x} \cdot 4}{8 \cdot 5}) + C$

Step 6.10.3.3.2.2

Cancel the common factor.

$e^{4 x} y = 3 (\frac{4 (\cos (2 x) e^{4 x})}{4 \cdot 5} + \frac{\sin (2 x) e^{4 x} \cdot 4}{8 \cdot 5}) + C$

Step 6.10.3.3.2.3

Rewrite the expression.

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{5} + \frac{\sin (2 x) e^{4 x} \cdot 4}{8 \cdot 5}) + C$

Step 6.10.3.4

Move $4$ to the left of $\sin (2 x) e^{4 x}$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{5} + \frac{4 \cdot (\sin (2 x) e^{4 x})}{8 \cdot 5}) + C$

Step 6.10.3.5

Multiply $8$ by $5$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{5} + \frac{4 \sin (2 x) e^{4 x}}{40}) + C$

Step 6.10.3.6

Cancel the common factor of $4$ and $40$ .

Tap for more steps...

Step 6.10.3.6.1

Factor $4$ out of $4 \sin (2 x) e^{4 x}$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{5} + \frac{4 (\sin (2 x) e^{4 x})}{40}) + C$

Step 6.10.3.6.2

Cancel the common factors.

Tap for more steps...

Step 6.10.3.6.2.1

Factor $4$ out of $40$ .

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{5} + \frac{4 (\sin (2 x) e^{4 x})}{4 \cdot 10}) + C$

Step 6.10.3.6.2.2

Cancel the common factor.

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{5} + \frac{4 (\sin (2 x) e^{4 x})}{4 \cdot 10}) + C$

Step 6.10.3.6.2.3

Rewrite the expression.

$e^{4 x} y = 3 (\frac{\cos (2 x) e^{4 x}}{5} + \frac{\sin (2 x) e^{4 x}}{10}) + C$

Step 6.10.4

Simplify.

Tap for more steps...

Step 6.10.4.1

Reorder factors in $\frac{\cos (2 x) e^{4 x}}{5}$ .

$e^{4 x} y = 3 (\frac{e^{4 x} \cos (2 x)}{5} + \frac{\sin (2 x) e^{4 x}}{10}) + C$

Step 6.10.4.2

Reorder factors in $\frac{\sin (2 x) e^{4 x}}{10}$ .

$e^{4 x} y = 3 (\frac{1}{5} e^{4 x} \cos (2 x) + \frac{1}{10} e^{4 x} \sin (2 x)) + C$

Step 7

Divide each term in $e^{4 x} y = 3 (\frac{1}{5} \cdot (e^{4 x} \cos (2 x)) + \frac{1}{10} \cdot (e^{4 x} \sin (2 x))) + C$ by $e^{4 x}$ and simplify.

Tap for more steps...

Step 7.1

Divide each term in $e^{4 x} y = 3 (\frac{1}{5} \cdot (e^{4 x} \cos (2 x)) + \frac{1}{10} \cdot (e^{4 x} \sin (2 x))) + C$ by $e^{4 x}$ .

$\frac{e^{4 x} y}{e^{4 x}} = \frac{3 (\frac{1}{5} \cdot (e^{4 x} \cos (2 x)) + \frac{1}{10} \cdot (e^{4 x} \sin (2 x)))}{e^{4 x}} + \frac{C}{e^{4 x}}$

Step 7.2

Simplify the left side.

Tap for more steps...

Step 7.2.1

Cancel the common factor of $e^{4 x}$ .

Tap for more steps...

Step 7.2.1.1

Cancel the common factor.

$\frac{e^{4 x} y}{e^{4 x}} = \frac{3 (\frac{1}{5} \cdot (e^{4 x} \cos (2 x)) + \frac{1}{10} \cdot (e^{4 x} \sin (2 x)))}{e^{4 x}} + \frac{C}{e^{4 x}}$

Step 7.2.1.2

Divide $y$ by $1$ .

$y = \frac{3 (\frac{1}{5} \cdot (e^{4 x} \cos (2 x)) + \frac{1}{10} \cdot (e^{4 x} \sin (2 x)))}{e^{4 x}} + \frac{C}{e^{4 x}}$

Step 7.3

Simplify the right side.

Tap for more steps...

Step 7.3.1

Simplify each term.

Tap for more steps...

Step 7.3.1.1

Simplify the numerator.

Tap for more steps...

Step 7.3.1.1.1

Factor $e^{4 x}$ out of $\frac{1}{5} \cdot e^{4 x} \cos (2 x) + \frac{1}{10} \cdot e^{4 x} \sin (2 x)$ .

Tap for more steps...

Step 7.3.1.1.1.1

Factor $e^{4 x}$ out of $\frac{1}{5} \cdot e^{4 x} \cos (2 x)$ .

$y = \frac{3 (e^{4 x} (\frac{1}{5} \cos (2 x)) + \frac{1}{10} \cdot e^{4 x} \sin (2 x))}{e^{4 x}} + \frac{C}{e^{4 x}}$

Step 7.3.1.1.1.2

Factor $e^{4 x}$ out of $\frac{1}{10} \cdot e^{4 x} \sin (2 x)$ .

$y = \frac{3 (e^{4 x} (\frac{1}{5} \cos (2 x)) + e^{4 x} (\frac{1}{10} \sin (2 x)))}{e^{4 x}} + \frac{C}{e^{4 x}}$

Step 7.3.1.1.1.3

Factor $e^{4 x}$ out of $e^{4 x} (\frac{1}{5} \cos (2 x)) + e^{4 x} (\frac{1}{10} \sin (2 x))$ .

$y = \frac{3 (e^{4 x} (\frac{1}{5} \cos (2 x) + \frac{1}{10} \sin (2 x)))}{e^{4 x}} + \frac{C}{e^{4 x}}$

Step 7.3.1.1.2

Combine $\frac{1}{5}$ and $\cos (2 x)$ .

$y = \frac{3 (e^{4 x} (\frac{\cos (2 x)}{5} + \frac{1}{10} \sin (2 x)))}{e^{4 x}} + \frac{C}{e^{4 x}}$

Step 7.3.1.1.3

Combine $\frac{1}{10}$ and $\sin (2 x)$ .

$y = \frac{3 e^{4 x} (\frac{\cos (2 x)}{5} + \frac{\sin (2 x)}{10})}{e^{4 x}} + \frac{C}{e^{4 x}}$

Step 7.3.1.2

Cancel the common factor of $e^{4 x}$ .

Tap for more steps...

Step 7.3.1.2.1

Cancel the common factor.

$y = \frac{3 e^{4 x} (\frac{\cos (2 x)}{5} + \frac{\sin (2 x)}{10})}{e^{4 x}} + \frac{C}{e^{4 x}}$

Step 7.3.1.2.2

Divide $3 (\frac{\cos (2 x)}{5} + \frac{\sin (2 x)}{10})$ by $1$ .

$y = 3 (\frac{\cos (2 x)}{5} + \frac{\sin (2 x)}{10}) + \frac{C}{e^{4 x}}$

Step 7.3.1.3

Apply the distributive property.

$y = 3 \frac{\cos (2 x)}{5} + 3 \frac{\sin (2 x)}{10} + \frac{C}{e^{4 x}}$

Step 7.3.1.4

Combine $3$ and $\frac{\cos (2 x)}{5}$ .

$y = \frac{3 \cos (2 x)}{5} + 3 \frac{\sin (2 x)}{10} + \frac{C}{e^{4 x}}$

Step 7.3.1.5

Combine $3$ and $\frac{\sin (2 x)}{10}$ .

$y = \frac{3 \cos (2 x)}{5} + \frac{3 \sin (2 x)}{10} + \frac{C}{e^{4 x}}$