Precalculus Examples

$15 {(x + 4)}^{4} - 23 {(x + 4)}^{2} = - 4$

Step 1

Simplify $15 {(x + 4)}^{4} - 23 {(x + 4)}^{2}$ .

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Step 1.1

Simplify each term.

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Step 1.1.1

Use the Binomial Theorem.

$15 (x^{4} + 4 x^{3} \cdot 4 + 6 x^{2} \cdot 4^{2} + 4 x \cdot 4^{3} + 4^{4}) - 23 {(x + 4)}^{2} = - 4$

Step 1.1.2

Simplify each term.

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Step 1.1.2.1

Multiply $4$ by $4$ .

$15 (x^{4} + 16 x^{3} + 6 x^{2} \cdot 4^{2} + 4 x \cdot 4^{3} + 4^{4}) - 23 {(x + 4)}^{2} = - 4$

Step 1.1.2.2

Raise $4$ to the power of $2$ .

$15 (x^{4} + 16 x^{3} + 6 x^{2} \cdot 16 + 4 x \cdot 4^{3} + 4^{4}) - 23 {(x + 4)}^{2} = - 4$

Step 1.1.2.3

Multiply $16$ by $6$ .

$15 (x^{4} + 16 x^{3} + 96 x^{2} + 4 x \cdot 4^{3} + 4^{4}) - 23 {(x + 4)}^{2} = - 4$

Step 1.1.2.4

Multiply $4$ by $4^{3}$ by adding the exponents.

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Step 1.1.2.4.1

Move $4^{3}$ .

$15 (x^{4} + 16 x^{3} + 96 x^{2} + 4^{3} \cdot 4 x + 4^{4}) - 23 {(x + 4)}^{2} = - 4$

Step 1.1.2.4.2

Multiply $4^{3}$ by $4$ .

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Step 1.1.2.4.2.1

Raise $4$ to the power of $1$ .

$15 (x^{4} + 16 x^{3} + 96 x^{2} + 4^{3} \cdot 4^{1} x + 4^{4}) - 23 {(x + 4)}^{2} = - 4$

Step 1.1.2.4.2.2

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

$15 (x^{4} + 16 x^{3} + 96 x^{2} + 4^{3 + 1} x + 4^{4}) - 23 {(x + 4)}^{2} = - 4$

Step 1.1.2.4.3

Add $3$ and $1$ .

$15 (x^{4} + 16 x^{3} + 96 x^{2} + 4^{4} x + 4^{4}) - 23 {(x + 4)}^{2} = - 4$

Step 1.1.2.5

Raise $4$ to the power of $4$ .

$15 (x^{4} + 16 x^{3} + 96 x^{2} + 256 x + 4^{4}) - 23 {(x + 4)}^{2} = - 4$

Step 1.1.2.6

Raise $4$ to the power of $4$ .

$15 (x^{4} + 16 x^{3} + 96 x^{2} + 256 x + 256) - 23 {(x + 4)}^{2} = - 4$

Step 1.1.3

Apply the distributive property.

$15 x^{4} + 15 (16 x^{3}) + 15 (96 x^{2}) + 15 (256 x) + 15 \cdot 256 - 23 {(x + 4)}^{2} = - 4$

Step 1.1.4

Simplify.

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Step 1.1.4.1

Multiply $16$ by $15$ .

$15 x^{4} + 240 x^{3} + 15 (96 x^{2}) + 15 (256 x) + 15 \cdot 256 - 23 {(x + 4)}^{2} = - 4$

Step 1.1.4.2

Multiply $96$ by $15$ .

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 15 (256 x) + 15 \cdot 256 - 23 {(x + 4)}^{2} = - 4$

Step 1.1.4.3

Multiply $256$ by $15$ .

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 15 \cdot 256 - 23 {(x + 4)}^{2} = - 4$

Step 1.1.4.4

Multiply $15$ by $256$ .

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 {(x + 4)}^{2} = - 4$

Step 1.1.5

Rewrite ${(x + 4)}^{2}$ as $(x + 4) (x + 4)$ .

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 ((x + 4) (x + 4)) = - 4$

Step 1.1.6

Expand $(x + 4) (x + 4)$ using the FOIL Method.

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Step 1.1.6.1

Apply the distributive property.

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 (x (x + 4) + 4 (x + 4)) = - 4$

Step 1.1.6.2

Apply the distributive property.

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 (x \cdot x + x \cdot 4 + 4 (x + 4)) = - 4$

Step 1.1.6.3

Apply the distributive property.

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 (x \cdot x + x \cdot 4 + 4 x + 4 \cdot 4) = - 4$

Step 1.1.7

Simplify and combine like terms.

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Step 1.1.7.1

Simplify each term.

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Step 1.1.7.1.1

Multiply $x$ by $x$ .

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 (x^{2} + x \cdot 4 + 4 x + 4 \cdot 4) = - 4$

Step 1.1.7.1.2

Move $4$ to the left of $x$ .

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 (x^{2} + 4 \cdot x + 4 x + 4 \cdot 4) = - 4$

Step 1.1.7.1.3

Multiply $4$ by $4$ .

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 (x^{2} + 4 x + 4 x + 16) = - 4$

Step 1.1.7.2

Add $4 x$ and $4 x$ .

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 (x^{2} + 8 x + 16) = - 4$

Step 1.1.8

Apply the distributive property.

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 x^{2} - 23 (8 x) - 23 \cdot 16 = - 4$

Step 1.1.9

Simplify.

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Step 1.1.9.1

Multiply $8$ by $- 23$ .

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 x^{2} - 184 x - 23 \cdot 16 = - 4$

Step 1.1.9.2

Multiply $- 23$ by $16$ .

$15 x^{4} + 240 x^{3} + 1440 x^{2} + 3840 x + 3840 - 23 x^{2} - 184 x - 368 = - 4$

Step 1.2

Simplify by adding terms.

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Step 1.2.1

Subtract $23 x^{2}$ from $1440 x^{2}$ .

$15 x^{4} + 240 x^{3} + 1417 x^{2} + 3840 x + 3840 - 184 x - 368 = - 4$

Step 1.2.2

Subtract $184 x$ from $3840 x$ .

$15 x^{4} + 240 x^{3} + 1417 x^{2} + 3656 x + 3840 - 368 = - 4$

Step 1.2.3

Subtract $368$ from $3840$ .

$15 x^{4} + 240 x^{3} + 1417 x^{2} + 3656 x + 3472 = - 4$

Step 2

Graph each side of the equation. The solution is the x-value of the point of intersection.

$x = - 4 - \frac{2 \sqrt{3}}{3}, - 4 - \frac{\sqrt{5}}{5}, - 4 + \frac{\sqrt{5}}{5}, - 4 + \frac{2 \sqrt{3}}{3}$

Step 3

The result can be shown in multiple forms.

Exact Form:

$x = - 4 - \frac{2 \sqrt{3}}{3}, - 4 - \frac{\sqrt{5}}{5}, - 4 + \frac{\sqrt{5}}{5}, - 4 + \frac{2 \sqrt{3}}{3}$

Decimal Form:

$x = - 5.15470053 \dots, - 4.44721359 \dots, - 3.55278640 \dots, - 2.84529946 \dots$

Step 4