Find the Equation Given the Roots square root of 5 , -1+i

$\sqrt{5}$ , $- 1 + i$

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 $x = \sqrt{5}$ was found by solving for $x$ when $x - (\sqrt{5}) = y$ and $y = 0$ .

The factor is $x - \sqrt{5}$

Step 3

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

The factor is $x + 1 - i$

Step 4

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

The factor is $x + 1 + i$

Step 5

Combine all the factors into a single equation.

$y = (x - \sqrt{5}) (x + 1 - i) (x + 1 + i)$

Step 6

Multiply all the factors to simplify the equation $y = (x - \sqrt{5}) (x + 1 - i) (x + 1 + i)$ .

Expand $(x - \sqrt{5}) (x + 1 - i)$ by multiplying each term in the first expression by each term in the second expression.

$y = (x \cdot x + x \cdot 1 + x (- i) - \sqrt{5} x - \sqrt{5} \cdot 1 - \sqrt{5} (- i)) (x + 1 + i)$

Simplify each term.

Multiply $x$ by $x$ .

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

Multiply $x$ by $1$ .

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

Multiply $- 1$ by $1$ .

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

Multiply $- \sqrt{5} (- i)$ .

Multiply $- 1$ by $- 1$ .

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

Multiply $\sqrt{5}$ by $1$ .

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

Expand $(x^{2} + x + x (- i) - \sqrt{5} x - \sqrt{5} + \sqrt{5} i) (x + 1 + i)$ by multiplying each term in the first expression by each term in the second expression.

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

Simplify terms.

Combine the opposite terms in $x^{2} x + x^{2} \cdot 1 + x^{2} i + x \cdot x + x \cdot 1 + x i + x (- i) x + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x i - \sqrt{5} x - \sqrt{5} \cdot 1 - \sqrt{5} i + \sqrt{5} i x + \sqrt{5} i \cdot 1 + \sqrt{5} i i$ .

Reorder the factors in the terms $- \sqrt{5} x i$ and $\sqrt{5} i x$ .

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

Add $- i x \sqrt{5}$ and $i x \sqrt{5}$ .

$y = x^{2} x + x^{2} \cdot 1 + x^{2} i + x \cdot x + x \cdot 1 + x i + x (- i) x + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 - \sqrt{5} i + 0 + \sqrt{5} i \cdot 1 + \sqrt{5} i i$

Add $x^{2} x + x^{2} \cdot 1 + x^{2} i + x \cdot x + x \cdot 1 + x i + x (- i) x + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 - \sqrt{5} i$ and $0$ .

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

Reorder the factors in the terms $- \sqrt{5} i$ and $\sqrt{5} i \cdot 1$ .

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

Add $- i \sqrt{5}$ and $1 i \sqrt{5}$ .

$y = x^{2} x + x^{2} \cdot 1 + x^{2} i + x \cdot x + x \cdot 1 + x i + x (- i) x + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + 0 + \sqrt{5} i i$

Add $x^{2} x + x^{2} \cdot 1 + x^{2} i + x \cdot x + x \cdot 1 + x i + x (- i) x + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1$ and $0$ .

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

Simplify each term.

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

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

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

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

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

Add $2$ and $1$ .

$y = x^{3} + x^{2} \cdot 1 + x^{2} i + x \cdot x + x \cdot 1 + x i + x (- i) x + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $x^{2}$ by $1$ .

$y = x^{3} + x^{2} + x^{2} i + x \cdot x + x \cdot 1 + x i + x (- i) x + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $x$ by $x$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x \cdot 1 + x i + x (- i) x + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $x$ by $1$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x (- i) x + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

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

Move $x$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x \cdot x (- i) + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $x$ by $x$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) \cdot 1 + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $x$ by $1$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x (- i) i - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $x (- i) i$ .

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

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x (- (i i)) - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

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

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x (- (i i)) - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

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

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x (- i^{1 + 1}) - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Add $1$ and $1$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x (- i^{2}) - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

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

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x (1) - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $- 1$ by $- 1$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x \cdot 1 - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $x$ by $1$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x - \sqrt{5} x \cdot x - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

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

Move $x$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x - \sqrt{5} (x \cdot x) - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $x$ by $x$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x - \sqrt{5} x^{2} - \sqrt{5} x \cdot 1 - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $- 1$ by $1$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} \cdot 1 + \sqrt{5} i i$

Multiply $- 1$ by $1$ .

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

Multiply $\sqrt{5} i i$ .

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

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

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

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

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

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} + \sqrt{5} i^{1 + 1}$

Add $1$ and $1$ .

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

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

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} + \sqrt{5} \cdot - 1$

Move $- 1$ to the left of $\sqrt{5}$ .

$y = x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} - 1 \cdot \sqrt{5}$

Rewrite $- 1 \sqrt{5}$ as $- \sqrt{5}$ .

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

Simplify by adding terms.

Combine the opposite terms in $x^{3} + x^{2} + x^{2} i + x^{2} + x + x i + x^{2} (- i) + x (- i) + x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} - \sqrt{5}$ .

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

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

Subtract $i x^{2}$ from $i x^{2}$ .

$y = x^{3} + x^{2} + x^{2} + x + x i + 0 + x (- i) + x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} - \sqrt{5}$

Add $x^{3} + x^{2} + x^{2} + x + x i$ and $0$ .

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

Reorder the factors in the terms $x i$ and $x (- i)$ .

$y = x^{3} + x^{2} + x^{2} + x + i x - i x + x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} - \sqrt{5}$

Subtract $i x$ from $i x$ .

$y = x^{3} + x^{2} + x^{2} + x + 0 + x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} - \sqrt{5}$

Add $x^{3} + x^{2} + x^{2} + x$ and $0$ .

$y = x^{3} + x^{2} + x^{2} + x + x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} - \sqrt{5}$

Add $x^{2}$ and $x^{2}$ .

$y = x^{3} + 2 x^{2} + x + x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} - \sqrt{5}$

Add $x$ and $x$ .

$y = x^{3} + 2 x^{2} + 2 x - \sqrt{5} x^{2} - \sqrt{5} x - \sqrt{5} x - \sqrt{5} - \sqrt{5}$

Subtract $\sqrt{5} x$ from $- \sqrt{5} x$ .

$y = x^{3} + 2 x^{2} + 2 x - \sqrt{5} x^{2} - 2 \sqrt{5} x - \sqrt{5} - \sqrt{5}$

Subtract $\sqrt{5}$ from $- \sqrt{5}$ .

$y = x^{3} + 2 x^{2} + 2 x - \sqrt{5} x^{2} - 2 \sqrt{5} x - 2 \sqrt{5}$

Move $2 x$ .

$y = x^{3} + 2 x^{2} - \sqrt{5} x^{2} + 2 x - 2 \sqrt{5} x - 2 \sqrt{5}$

Step 7

Find the Equation Given the Roots square root of 5 , -1+i

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