Evaluate (7-i)/(3+i)

$\frac{7 - i}{3 + i}$

Step 1

Multiply the numerator and denominator of $\frac{7 - i}{3 + 1 i}$ by the conjugate of $3 + 1 i$ to make the denominator real.

$\frac{7 - i}{3 + 1 i} \cdot \frac{3 - i}{3 - i}$

Step 2

Multiply.

Combine.

$\frac{(7 - i) (3 - i)}{(3 + 1 i) (3 - i)}$

Simplify the numerator.

Expand $(7 - i) (3 - i)$ using the FOIL Method.

Apply the distributive property.

$\frac{7 (3 - i) - i (3 - i)}{(3 + 1 i) (3 - i)}$

Apply the distributive property.

$\frac{7 \cdot 3 + 7 (- i) - i (3 - i)}{(3 + 1 i) (3 - i)}$

Apply the distributive property.

$\frac{7 \cdot 3 + 7 (- i) - i \cdot 3 - i (- i)}{(3 + 1 i) (3 - i)}$

Simplify and combine like terms.

Simplify each term.

Multiply $7$ by $3$ .

$\frac{21 + 7 (- i) - i \cdot 3 - i (- i)}{(3 + 1 i) (3 - i)}$

Multiply $- 1$ by $7$ .

$\frac{21 - 7 i - i \cdot 3 - i (- i)}{(3 + 1 i) (3 - i)}$

Multiply $3$ by $- 1$ .

$\frac{21 - 7 i - 3 i - i (- i)}{(3 + 1 i) (3 - i)}$

Multiply $- i (- i)$ .

Multiply $- 1$ by $- 1$ .

$\frac{21 - 7 i - 3 i + 1 i i}{(3 + 1 i) (3 - i)}$

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

$\frac{21 - 7 i - 3 i + 1 (i^{1} i)}{(3 + 1 i) (3 - i)}$

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

$\frac{21 - 7 i - 3 i + 1 (i^{1} i^{1})}{(3 + 1 i) (3 - i)}$

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

$\frac{21 - 7 i - 3 i + 1 i^{1 + 1}}{(3 + 1 i) (3 - i)}$

Add $1$ and $1$ .

$\frac{21 - 7 i - 3 i + 1 i^{2}}{(3 + 1 i) (3 - i)}$

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

$\frac{21 - 7 i - 3 i + i^{2}}{(3 + 1 i) (3 - i)}$

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

$\frac{21 - 7 i - 3 i - 1}{(3 + 1 i) (3 - i)}$

Subtract $1$ from $21$ .

$\frac{20 - 7 i - 3 i}{(3 + 1 i) (3 - i)}$

Subtract $3 i$ from $- 7 i$ .

$\frac{20 - 10 i}{(3 + 1 i) (3 - i)}$

Simplify the denominator.

Expand $(3 + 1 i) (3 - i)$ using the FOIL Method.

Apply the distributive property.

$\frac{20 - 10 i}{3 (3 - i) + 1 i (3 - i)}$

Apply the distributive property.

$\frac{20 - 10 i}{3 \cdot 3 + 3 (- i) + 1 i (3 - i)}$

Apply the distributive property.

$\frac{20 - 10 i}{3 \cdot 3 + 3 (- i) + 1 i \cdot 3 + 1 i (- i)}$

Simplify.

Multiply $3$ by $3$ .

$\frac{20 - 10 i}{9 + 3 (- i) + 1 i \cdot 3 + 1 i (- i)}$

Multiply $- 1$ by $3$ .

$\frac{20 - 10 i}{9 - 3 i + 1 i \cdot 3 + 1 i (- i)}$

Multiply $3$ by $1$ .

$\frac{20 - 10 i}{9 - 3 i + 3 i + 1 i (- i)}$

Multiply $- 1$ by $1$ .

$\frac{20 - 10 i}{9 - 3 i + 3 i - i i}$

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

$\frac{20 - 10 i}{9 - 3 i + 3 i - (i^{1} i)}$

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

$\frac{20 - 10 i}{9 - 3 i + 3 i - (i^{1} i^{1})}$

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

$\frac{20 - 10 i}{9 - 3 i + 3 i - i^{1 + 1}}$

Add $1$ and $1$ .

$\frac{20 - 10 i}{9 - 3 i + 3 i - i^{2}}$

Add $- 3 i$ and $3 i$ .

$\frac{20 - 10 i}{9 + 0 - i^{2}}$

Add $9$ and $0$ .

$\frac{20 - 10 i}{9 - i^{2}}$

Simplify each term.

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

$\frac{20 - 10 i}{9 - - 1}$

Multiply $- 1$ by $- 1$ .

$\frac{20 - 10 i}{9 + 1}$

Add $9$ and $1$ .

$\frac{20 - 10 i}{10}$

Step 3

Cancel the common factor of $20 - 10 i$ and $10$ .

Factor $10$ out of $20$ .

$\frac{10 \cdot 2 - 10 i}{10}$

Factor $10$ out of $- 10 i$ .

$\frac{10 \cdot 2 + 10 (- i)}{10}$

Factor $10$ out of $10 (2) + 10 (- i)$ .

$\frac{10 (2 - i)}{10}$

Cancel the common factors.

Factor $10$ out of $10$ .

$\frac{10 (2 - i)}{10 (1)}$

Cancel the common factor.

$\frac{10 (2 - i)}{10 \cdot 1}$

Rewrite the expression.

$\frac{2 - i}{1}$

Divide $2 - i$ by $1$ .

$2 - i$

Evaluate (7-i)/(3+i)

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