Algebra Examples

$3 x^{5} + 6 x^{4} - 72 x^{3} = 0$

Step 1

Factor the left side of the equation.

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Step 1.1

Factor $3 x^{3}$ out of $3 x^{5} + 6 x^{4} - 72 x^{3}$ .

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Step 1.1.1

Factor $3 x^{3}$ out of $3 x^{5}$ .

$3 x^{3} (x^{2}) + 6 x^{4} - 72 x^{3} = 0$

Step 1.1.2

Factor $3 x^{3}$ out of $6 x^{4}$ .

$3 x^{3} (x^{2}) + 3 x^{3} (2 x) - 72 x^{3} = 0$

Step 1.1.3

Factor $3 x^{3}$ out of $- 72 x^{3}$ .

$3 x^{3} (x^{2}) + 3 x^{3} (2 x) + 3 x^{3} (- 24) = 0$

Step 1.1.4

Factor $3 x^{3}$ out of $3 x^{3} (x^{2}) + 3 x^{3} (2 x)$ .

$3 x^{3} (x^{2} + 2 x) + 3 x^{3} (- 24) = 0$

Step 1.1.5

Factor $3 x^{3}$ out of $3 x^{3} (x^{2} + 2 x) + 3 x^{3} (- 24)$ .

$3 x^{3} (x^{2} + 2 x - 24) = 0$

Step 1.2

Factor.

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Step 1.2.1

Factor $x^{2} + 2 x - 24$ using the AC method.

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Step 1.2.1.1

Consider the form $x^{2} + b x + c$ . Find a pair of integers whose product is $c$ and whose sum is $b$ . In this case, whose product is $- 24$ and whose sum is $2$ .

$- 4, 6$

Step 1.2.1.2

Write the factored form using these integers.

$3 x^{3} ((x - 4) (x + 6)) = 0$

Step 1.2.2

Remove unnecessary parentheses.

$3 x^{3} (x - 4) (x + 6) = 0$

Step 2

If any individual factor on the left side of the equation is equal to $0$ , the entire expression will be equal to $0$ .

$x^{3} = 0$

$x - 4 = 0$

$x + 6 = 0$

Step 3

Set $x^{3}$ equal to $0$ and solve for $x$ .

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Step 3.1

Set $x^{3}$ equal to $0$ .

$x^{3} = 0$

Step 3.2

Solve $x^{3} = 0$ for $x$ .

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Step 3.2.1

Take the specified root of both sides of the equation to eliminate the exponent on the left side.

$x = \sqrt[3]{0}$

Step 3.2.2

Simplify $\sqrt[3]{0}$ .

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Step 3.2.2.1

Rewrite $0$ as $0^{3}$ .

$x = \sqrt[3]{0^{3}}$

Step 3.2.2.2

Pull terms out from under the radical, assuming real numbers.

$x = 0$

Step 4

Set $x - 4$ equal to $0$ and solve for $x$ .

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Step 4.1

Set $x - 4$ equal to $0$ .

$x - 4 = 0$

Step 4.2

Add $4$ to both sides of the equation.

$x = 4$

Step 5

Set $x + 6$ equal to $0$ and solve for $x$ .

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Step 5.1

Set $x + 6$ equal to $0$ .

$x + 6 = 0$

Step 5.2

Subtract $6$ from both sides of the equation.

$x = - 6$

Step 6

The final solution is all the values that make $3 x^{3} (x - 4) (x + 6) = 0$ true.

$x = 0, 4, - 6$

Step 7