Calculus Examples

$f (x) = - 3 x^{4} + 7 x^{2} - 4$ , $(1, 0)$

Step 1

Find the first derivative and evaluate at $x = 1$ and $y = 0$ to find the slope of the tangent line.

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Step 1.1

By the Sum Rule, the derivative of $- 3 x^{4} + 7 x^{2} - 4$ with respect to $x$ is $\frac{d}{d x} [- 3 x^{4}] + \frac{d}{d x} [7 x^{2}] + \frac{d}{d x} [- 4]$ .

$\frac{d}{d x} [- 3 x^{4}] + \frac{d}{d x} [7 x^{2}] + \frac{d}{d x} [- 4]$

Step 1.2

Evaluate $\frac{d}{d x} [- 3 x^{4}]$ .

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Step 1.2.1

Since $- 3$ is constant with respect to $x$ , the derivative of $- 3 x^{4}$ with respect to $x$ is $- 3 \frac{d}{d x} [x^{4}]$ .

$- 3 \frac{d}{d x} [x^{4}] + \frac{d}{d x} [7 x^{2}] + \frac{d}{d x} [- 4]$

Step 1.2.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 4$ .

$- 3 (4 x^{3}) + \frac{d}{d x} [7 x^{2}] + \frac{d}{d x} [- 4]$

Step 1.2.3

Multiply $4$ by $- 3$ .

$- 12 x^{3} + \frac{d}{d x} [7 x^{2}] + \frac{d}{d x} [- 4]$

Step 1.3

Evaluate $\frac{d}{d x} [7 x^{2}]$ .

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Step 1.3.1

Since $7$ is constant with respect to $x$ , the derivative of $7 x^{2}$ with respect to $x$ is $7 \frac{d}{d x} [x^{2}]$ .

$- 12 x^{3} + 7 \frac{d}{d x} [x^{2}] + \frac{d}{d x} [- 4]$

Step 1.3.2

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

$- 12 x^{3} + 7 (2 x) + \frac{d}{d x} [- 4]$

Step 1.3.3

Multiply $2$ by $7$ .

$- 12 x^{3} + 14 x + \frac{d}{d x} [- 4]$

Step 1.4

Differentiate using the Constant Rule.

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Step 1.4.1

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

$- 12 x^{3} + 14 x + 0$

Step 1.4.2

Add $- 12 x^{3} + 14 x$ and $0$ .

$- 12 x^{3} + 14 x$

Step 1.5

Evaluate the derivative at $x = 1$ .

$- 12 {(1)}^{3} + 14 (1)$

Step 1.6

Simplify.

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Step 1.6.1

Simplify each term.

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Step 1.6.1.1

One to any power is one.

$- 12 \cdot 1 + 14 (1)$

Step 1.6.1.2

Multiply $- 12$ by $1$ .

$- 12 + 14 (1)$

Step 1.6.1.3

Multiply $14$ by $1$ .

$- 12 + 14$

Step 1.6.2

Add $- 12$ and $14$ .

$2$

Step 2

Plug the slope and point values into the point-slope formula and solve for $y$ .

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Step 2.1

Use the slope $2$ and a given point $(1, 0)$ to substitute for $x_{1}$ and $y_{1}$ in the point-slope form $y - y_{1} = m (x - x_{1})$ , which is derived from the slope equation $m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}}$ .

$y - (0) = 2 \cdot (x - (1))$

Step 2.2

Simplify the equation and keep it in point-slope form.

$y + 0 = 2 \cdot (x - 1)$

Step 2.3

Solve for $y$ .

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Step 2.3.1

Add $y$ and $0$ .

$y = 2 \cdot (x - 1)$

Step 2.3.2

Simplify $2 \cdot (x - 1)$ .

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Step 2.3.2.1

Apply the distributive property.

$y = 2 x + 2 \cdot - 1$

Step 2.3.2.2

Multiply $2$ by $- 1$ .

$y = 2 x - 2$

Step 3