Simplify -3i(7i-5)

$- 3 i (7 i - 5)$

Step 1

Apply the distributive property.

$- 3 i (7 i) - 3 i \cdot - 5$

Step 2

Multiply $- 3 i (7 i)$ .

Multiply $7$ by $- 3$ .

$- 21 i i - 3 i \cdot - 5$

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

$- 21 (i^{1} i) - 3 i \cdot - 5$

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

$- 21 (i^{1} i^{1}) - 3 i \cdot - 5$

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

$- 21 i^{1 + 1} - 3 i \cdot - 5$

Add $1$ and $1$ .

$- 21 i^{2} - 3 i \cdot - 5$

Step 3

Multiply $- 5$ by $- 3$ .

$- 21 i^{2} + 15 i$

Step 4

Simplify each term.

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

$- 21 \cdot - 1 + 15 i$

Multiply $- 21$ by $- 1$ .

$21 + 15 i$