Precalculus Examples

$- 1$ , $6 - 7 i$

Step 1

Roots are the points where the graph intercepts with the x-axis $(y = 0)$ .

$y = 0$ at the roots

Step 2

The root at $x = - 1$ was found by solving for $x$ when $x - (- 1) = y$ and $y = 0$ .

The factor is $x + 1$

Step 3

The root at $x = 6 - 7 i$ was found by solving for $x$ when $x - (6 - 7 i) = y$ and $y = 0$ .

The factor is $x - 6 + 7 i$

Step 4

The root at $x = 6 + 7 i$ was found by solving for $x$ when $x - (6 + 7 i) = y$ and $y = 0$ .

The factor is $x - 6 - 7 i$

Step 5

Combine all the factors into a single equation.

$y = (x + 1) (x - 6 + 7 i) (x - 6 - 7 i)$

Step 6

Multiply all the factors to simplify the equation $y = (x + 1) (x - 6 + 7 i) (x - 6 - 7 i)$ .

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Step 6.1

Expand $(x + 1) (x - 6 + 7 i)$ by multiplying each term in the first expression by each term in the second expression.

$y = (x \cdot x + x \cdot - 6 + x (7 i) + 1 x + 1 \cdot - 6 + 1 (7 i)) (x - 6 - 7 i)$

Step 6.2

Simplify terms.

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Step 6.2.1

Simplify each term.

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Step 6.2.1.1

Multiply $x$ by $x$ .

$y = (x^{2} + x \cdot - 6 + x (7 i) + 1 x + 1 \cdot - 6 + 1 (7 i)) (x - 6 - 7 i)$

Step 6.2.1.2

Move $- 6$ to the left of $x$ .

$y = (x^{2} - 6 \cdot x + x (7 i) + 1 x + 1 \cdot - 6 + 1 (7 i)) (x - 6 - 7 i)$

Step 6.2.1.3

Move $7$ to the left of $x$ .

$y = (x^{2} - 6 x + 7 \cdot (x i) + 1 x + 1 \cdot - 6 + 1 (7 i)) (x - 6 - 7 i)$

Step 6.2.1.4

Multiply $x$ by $1$ .

$y = (x^{2} - 6 x + 7 x i + x + 1 \cdot - 6 + 1 (7 i)) (x - 6 - 7 i)$

Step 6.2.1.5

Multiply $- 6$ by $1$ .

$y = (x^{2} - 6 x + 7 x i + x - 6 + 1 (7 i)) (x - 6 - 7 i)$

Step 6.2.1.6

Multiply $7 i$ by $1$ .

$y = (x^{2} - 6 x + 7 x i + x - 6 + 7 i) (x - 6 - 7 i)$

Step 6.2.2

Add $- 6 x$ and $x$ .

$y = (x^{2} + 7 x i - 5 x - 6 + 7 i) (x - 6 - 7 i)$

Step 6.3

Expand $(x^{2} + 7 x i - 5 x - 6 + 7 i) (x - 6 - 7 i)$ by multiplying each term in the first expression by each term in the second expression.

$y = x^{2} x + x^{2} \cdot - 6 + x^{2} (- 7 i) + 7 x i x + 7 x i \cdot - 6 + 7 x i (- 7 i) - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4

Simplify terms.

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Step 6.4.1

Simplify each term.

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Step 6.4.1.1

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

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Step 6.4.1.1.1

Multiply $x^{2}$ by $x$ .

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Step 6.4.1.1.1.1

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

Step 6.4.1.1.1.2

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

$y = x^{2 + 1} + x^{2} \cdot - 6 + x^{2} (- 7 i) + 7 x i x + 7 x i \cdot - 6 + 7 x i (- 7 i) - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.1.2

Add $2$ and $1$ .

$y = x^{3} + x^{2} \cdot - 6 + x^{2} (- 7 i) + 7 x i x + 7 x i \cdot - 6 + 7 x i (- 7 i) - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.2

Move $- 6$ to the left of $x^{2}$ .

$y = x^{3} - 6 \cdot x^{2} + x^{2} (- 7 i) + 7 x i x + 7 x i \cdot - 6 + 7 x i (- 7 i) - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.3

Multiply $x$ by $x$ by adding the exponents.

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Step 6.4.1.3.1

Move $x$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 (x \cdot x) i + 7 x i \cdot - 6 + 7 x i (- 7 i) - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.3.2

Multiply $x$ by $x$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i + 7 x i \cdot - 6 + 7 x i (- 7 i) - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.4

Multiply $- 6$ by $7$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 7 x i (- 7 i) - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.5

Multiply $7 x i (- 7 i)$ .

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Step 6.4.1.5.1

Multiply $- 7$ by $7$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i - 49 x i i - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.5.2

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

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i - 49 x (i i) - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.5.3

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

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i - 49 x (i i) - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.5.4

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

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i - 49 x i^{1 + 1} - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.5.5

Add $1$ and $1$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i - 49 x i^{2} - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.6

Rewrite $i^{2}$ as $- 1$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i - 49 x \cdot - 1 - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.7

Multiply $- 1$ by $- 49$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x \cdot x - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.8

Multiply $x$ by $x$ by adding the exponents.

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Step 6.4.1.8.1

Move $x$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 (x \cdot x) - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.8.2

Multiply $x$ by $x$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} - 5 x \cdot - 6 - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.9

Multiply $- 6$ by $- 5$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x - 5 x (- 7 i) - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.10

Multiply $- 7$ by $- 5$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x - 6 \cdot - 6 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.11

Multiply $- 6$ by $- 6$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 - 6 (- 7 i) + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.12

Multiply $- 7$ by $- 6$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x + 7 i \cdot - 6 + 7 i (- 7 i)$

Step 6.4.1.13

Multiply $- 6$ by $7$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i + 7 i (- 7 i)$

Step 6.4.1.14

Multiply $7 i (- 7 i)$ .

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Step 6.4.1.14.1

Multiply $- 7$ by $7$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i - 49 i i$

Step 6.4.1.14.2

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

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i - 49 (i i)$

Step 6.4.1.14.3

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

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i - 49 (i i)$

Step 6.4.1.14.4

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

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i - 49 i^{1 + 1}$

Step 6.4.1.14.5

Add $1$ and $1$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i - 49 i^{2}$

Step 6.4.1.15

Rewrite $i^{2}$ as $- 1$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i - 49 \cdot - 1$

Step 6.4.1.16

Multiply $- 49$ by $- 1$ .

$y = x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i + 49$

Step 6.4.2

Simplify by adding terms.

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Step 6.4.2.1

Combine the opposite terms in $x^{3} - 6 x^{2} + x^{2} (- 7 i) + 7 x^{2} i - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i + 49$ .

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Step 6.4.2.1.1

Reorder the factors in the terms $x^{2} (- 7 i)$ and $7 x^{2} i$ .

$y = x^{3} - 6 x^{2} - 7 i x^{2} + 7 i x^{2} - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i + 49$

Step 6.4.2.1.2

Add $- 7 i x^{2}$ and $7 i x^{2}$ .

$y = x^{3} - 6 x^{2} + 0 - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i + 49$

Step 6.4.2.1.3

Add $x^{3} - 6 x^{2}$ and $0$ .

$y = x^{3} - 6 x^{2} - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 42 i + 7 i x - 42 i + 49$

Step 6.4.2.1.4

Subtract $42 i$ from $42 i$ .

$y = x^{3} - 6 x^{2} - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 7 i x + 0 + 49$

Step 6.4.2.1.5

Add $x^{3} - 6 x^{2} - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 7 i x$ and $0$ .

$y = x^{3} - 6 x^{2} - 42 x i + 49 x - 5 x^{2} + 30 x + 35 x i - 6 x + 36 + 7 i x + 49$

Step 6.4.2.2

Subtract $5 x^{2}$ from $- 6 x^{2}$ .

$y = x^{3} - 11 x^{2} - 42 x i + 49 x + 30 x + 35 x i - 6 x + 36 + 7 i x + 49$

Step 6.4.2.3

Add $- 42 x i$ and $35 x i$ .

$y = x^{3} - 11 x^{2} - 7 x i + 49 x + 30 x - 6 x + 36 + 7 i x + 49$

Step 6.4.2.4

Combine the opposite terms in $x^{3} - 11 x^{2} - 7 x i + 49 x + 30 x - 6 x + 36 + 7 i x + 49$ .

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Step 6.4.2.4.1

Reorder the factors in the terms $- 7 x i$ and $7 i x$ .

$y = x^{3} - 11 x^{2} - 7 i x + 49 x + 30 x - 6 x + 36 + 7 i x + 49$

Step 6.4.2.4.2

Add $- 7 i x$ and $7 i x$ .

$y = x^{3} - 11 x^{2} + 49 x + 30 x - 6 x + 36 + 0 + 49$

Step 6.4.2.4.3

Add $x^{3} - 11 x^{2} + 49 x + 30 x - 6 x + 36$ and $0$ .

$y = x^{3} - 11 x^{2} + 49 x + 30 x - 6 x + 36 + 49$

Step 6.4.2.5

Add $49 x$ and $30 x$ .

$y = x^{3} - 11 x^{2} + 79 x - 6 x + 36 + 49$

Step 6.4.2.6

Subtract $6 x$ from $79 x$ .

$y = x^{3} - 11 x^{2} + 73 x + 36 + 49$

Step 6.4.2.7

Add $36$ and $49$ .

$y = x^{3} - 11 x^{2} + 73 x + 85$

Step 7