Find dy/dx y=-x^3(3x^4-2)

$y = - x^{3} (3 x^{4} - 2)$

Step 1

Differentiate both sides of the equation.

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

Step 2

The derivative of $y$ with respect to $x$ is $y'$ .

$y'$

Step 3

Differentiate the right side of the equation.

Since $- 1$ is constant with respect to $x$ , the derivative of $- x^{3} (3 x^{4} - 2)$ with respect to $x$ is $- \frac{d}{d x} [x^{3} (3 x^{4} - 2)]$ .

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

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{3}$ and $g (x) = 3 x^{4} - 2$ .

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

Differentiate.

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

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

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

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

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

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

Multiply $4$ by $3$ .

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

Since $- 2$ is constant with respect to $x$ , the derivative of $- 2$ with respect to $x$ is $0$ .

$- (x^{3} (12 x^{3} + 0) + (3 x^{4} - 2) \frac{d}{d x} [x^{3}])$

Add $12 x^{3}$ and $0$ .

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

Multiply $x^{3}$ by $x^{3}$ by adding the exponents.

Move $x^{3}$ .

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

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

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

Add $3$ and $3$ .

$- (x^{6} \cdot 12 + (3 x^{4} - 2) \frac{d}{d x} [x^{3}])$

Move $12$ to the left of $x^{6}$ .

$- (12 \cdot x^{6} + (3 x^{4} - 2) \frac{d}{d x} [x^{3}])$

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 3$ .

$- (12 x^{6} + (3 x^{4} - 2) (3 x^{2}))$

Move $3$ to the left of $3 x^{4} - 2$ .

$- (12 x^{6} + 3 \cdot (3 x^{4} - 2) x^{2})$

Simplify.

Apply the distributive property.

$- (12 x^{6} + (3 (3 x^{4}) + 3 \cdot - 2) x^{2})$

Apply the distributive property.

$- (12 x^{6} + 3 (3 x^{4}) x^{2} + 3 \cdot - 2 x^{2})$

Apply the distributive property.

$- (12 x^{6}) - (3 (3 x^{4}) x^{2}) - (3 \cdot - 2 x^{2})$

Combine terms.

Multiply $12$ by $- 1$ .

$- 12 x^{6} - (3 (3 x^{4}) x^{2}) - (3 \cdot - 2 x^{2})$

Multiply $3$ by $3$ .

$- 12 x^{6} - (9 x^{4} x^{2}) - (3 \cdot - 2 x^{2})$

Multiply $x^{4}$ by $x^{2}$ by adding the exponents.

Move $x^{2}$ .

$- 12 x^{6} - (9 (x^{2} x^{4})) - (3 \cdot - 2 x^{2})$

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

$- 12 x^{6} - (9 x^{2 + 4}) - (3 \cdot - 2 x^{2})$

Add $2$ and $4$ .

$- 12 x^{6} - (9 x^{6}) - (3 \cdot - 2 x^{2})$

Multiply $9$ by $- 1$ .

$- 12 x^{6} - 9 x^{6} - (3 \cdot - 2 x^{2})$

Multiply $3$ by $- 2$ .

$- 12 x^{6} - 9 x^{6} - (- 6 x^{2})$

Multiply $- 6$ by $- 1$ .

$- 12 x^{6} - 9 x^{6} + 6 x^{2}$

Subtract $9 x^{6}$ from $- 12 x^{6}$ .

$- 21 x^{6} + 6 x^{2}$

Step 4

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

$y' = - 21 x^{6} + 6 x^{2}$

Step 5

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

$\frac{d y}{d x} = - 21 x^{6} + 6 x^{2}$

Find dy/dx y=-x^3(3x^4-2)

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