Calculus Examples

$r (t) = (t + e^{t}) (4 - \sqrt{t})$

Step 1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{t}$ as $t^{\frac{1}{2}}$ .

$\frac{d}{d t} [(t + e^{t}) (4 - t^{\frac{1}{2}})]$

Step 2

Differentiate using the Product Rule which states that $\frac{d}{d t} [f (t) g (t)]$ is $f (t) \frac{d}{d t} [g (t)] + g (t) \frac{d}{d t} [f (t)]$ where $f (t) = t + e^{t}$ and $g (t) = 4 - t^{\frac{1}{2}}$ .

$(t + e^{t}) \frac{d}{d t} [4 - t^{\frac{1}{2}}] + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 3

Differentiate.

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Step 3.1

By the Sum Rule, the derivative of $4 - t^{\frac{1}{2}}$ with respect to $t$ is $\frac{d}{d t} [4] + \frac{d}{d t} [- t^{\frac{1}{2}}]$ .

$(t + e^{t}) (\frac{d}{d t} [4] + \frac{d}{d t} [- t^{\frac{1}{2}}]) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 3.2

Since $4$ is constant with respect to $t$ , the derivative of $4$ with respect to $t$ is $0$ .

$(t + e^{t}) (0 + \frac{d}{d t} [- t^{\frac{1}{2}}]) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 3.3

Add $0$ and $\frac{d}{d t} [- t^{\frac{1}{2}}]$ .

$(t + e^{t}) \frac{d}{d t} [- t^{\frac{1}{2}}] + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 3.4

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

$(t + e^{t}) (- \frac{d}{d t} [t^{\frac{1}{2}}]) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 3.5

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

$(t + e^{t}) (- (\frac{1}{2} t^{\frac{1}{2} - 1})) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 4

To write $- 1$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

$(t + e^{t}) (- (\frac{1}{2} t^{\frac{1}{2} - 1 \cdot \frac{2}{2}})) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 5

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

$(t + e^{t}) (- (\frac{1}{2} t^{\frac{1}{2} + \frac{- 1 \cdot 2}{2}})) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 6

Combine the numerators over the common denominator.

$(t + e^{t}) (- (\frac{1}{2} t^{\frac{1 - 1 \cdot 2}{2}})) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 7

Simplify the numerator.

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Step 7.1

Multiply $- 1$ by $2$ .

$(t + e^{t}) (- (\frac{1}{2} t^{\frac{1 - 2}{2}})) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 7.2

Subtract $2$ from $1$ .

$(t + e^{t}) (- (\frac{1}{2} t^{\frac{- 1}{2}})) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 8

Differentiate.

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Step 8.1

Move the negative in front of the fraction.

$(t + e^{t}) (- (\frac{1}{2} t^{- \frac{1}{2}})) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 8.2

Combine fractions.

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Step 8.2.1

Combine $\frac{1}{2}$ and $t^{- \frac{1}{2}}$ .

$(t + e^{t}) (- \frac{t^{- \frac{1}{2}}}{2}) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 8.2.2

Move $t^{- \frac{1}{2}}$ to the denominator using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$(t + e^{t}) (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) \frac{d}{d t} [t + e^{t}]$

Step 8.3

By the Sum Rule, the derivative of $t + e^{t}$ with respect to $t$ is $\frac{d}{d t} [t] + \frac{d}{d t} [e^{t}]$ .

$(t + e^{t}) (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (\frac{d}{d t} [t] + \frac{d}{d t} [e^{t}])$

Step 8.4

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

$(t + e^{t}) (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (1 + \frac{d}{d t} [e^{t}])$

Step 9

Differentiate using the Exponential Rule which states that $\frac{d}{d t} [a^{t}]$ is $a^{t} \ln (a)$ where $a$ = $e$ .

$(t + e^{t}) (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (1 + e^{t})$

Step 10

Simplify.

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Step 10.1

Apply the distributive property.

$t (- \frac{1}{2 t^{\frac{1}{2}}}) + e^{t} (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (1 + e^{t})$

Step 10.2

Combine terms.

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Step 10.2.1

Combine $t$ and $\frac{1}{2 t^{\frac{1}{2}}}$ .

$- \frac{t}{2 t^{\frac{1}{2}}} + e^{t} (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (1 + e^{t})$

Step 10.2.2

Move $t^{\frac{1}{2}}$ to the numerator using the negative exponent rule $\frac{1}{b^{n}} = b^{- n}$ .

$- \frac{t \cdot t^{- \frac{1}{2}}}{2} + e^{t} (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (1 + e^{t})$

Step 10.2.3

Multiply $t$ by $t^{- \frac{1}{2}}$ by adding the exponents.

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Step 10.2.3.1

Multiply $t$ by $t^{- \frac{1}{2}}$ .

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Step 10.2.3.1.1

Raise $t$ to the power of $1$ .

$- \frac{t^{1} t^{- \frac{1}{2}}}{2} + e^{t} (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (1 + e^{t})$

Step 10.2.3.1.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$- \frac{t^{1 - \frac{1}{2}}}{2} + e^{t} (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (1 + e^{t})$

Step 10.2.3.2

Write $1$ as a fraction with a common denominator.

$- \frac{t^{\frac{2}{2} - \frac{1}{2}}}{2} + e^{t} (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (1 + e^{t})$

Step 10.2.3.3

Combine the numerators over the common denominator.

$- \frac{t^{\frac{2 - 1}{2}}}{2} + e^{t} (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (1 + e^{t})$

Step 10.2.3.4

Subtract $1$ from $2$ .

$- \frac{t^{\frac{1}{2}}}{2} + e^{t} (- \frac{1}{2 t^{\frac{1}{2}}}) + (4 - t^{\frac{1}{2}}) (1 + e^{t})$

Step 10.2.4

Combine $e^{t}$ and $\frac{1}{2 t^{\frac{1}{2}}}$ .

$- \frac{t^{\frac{1}{2}}}{2} - \frac{e^{t}}{2 t^{\frac{1}{2}}} + (4 - t^{\frac{1}{2}}) (1 + e^{t})$

Step 10.2.5

To write $(4 - t^{\frac{1}{2}}) (1 + e^{t})$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

$- \frac{t^{\frac{1}{2}}}{2} + (4 - t^{\frac{1}{2}}) (1 + e^{t}) \cdot \frac{2}{2} - \frac{e^{t}}{2 t^{\frac{1}{2}}}$

Step 10.2.6

Combine $(4 - t^{\frac{1}{2}}) (1 + e^{t})$ and $\frac{2}{2}$ .

$- \frac{t^{\frac{1}{2}}}{2} + \frac{(4 - t^{\frac{1}{2}}) (1 + e^{t}) \cdot 2}{2} - \frac{e^{t}}{2 t^{\frac{1}{2}}}$

Step 10.2.7

Combine the numerators over the common denominator.

$\frac{- t^{\frac{1}{2}} + (4 - t^{\frac{1}{2}}) (1 + e^{t}) \cdot 2}{2} - \frac{e^{t}}{2 t^{\frac{1}{2}}}$

Step 10.2.8

Move $2$ to the left of $(4 - t^{\frac{1}{2}}) (1 + e^{t})$ .

$\frac{- t^{\frac{1}{2}} + 2 (4 - t^{\frac{1}{2}}) (1 + e^{t})}{2} - \frac{e^{t}}{2 t^{\frac{1}{2}}}$