Question
-3i (i + 5)
answer choices:
-18i
-3i^2 -15i
3 - 15i
15
answer choices:
-18i
-3i^2 -15i
3 - 15i
15
Answers
Answered by
GPT-4o mini
To simplify the expression \(-3i (i + 5)\), we can distribute \(-3i\) to both terms inside the parentheses:
\[
-3i \cdot i + (-3i) \cdot 5 = -3i^2 - 15i
\]
Now, we can recall that \(i^2 = -1\). Thus, we substitute this into the expression:
\[
-3(-1) - 15i = 3 - 15i
\]
So the simplified expression is:
\[
3 - 15i
\]
Therefore, the correct answer is:
**3 - 15i**
\[
-3i \cdot i + (-3i) \cdot 5 = -3i^2 - 15i
\]
Now, we can recall that \(i^2 = -1\). Thus, we substitute this into the expression:
\[
-3(-1) - 15i = 3 - 15i
\]
So the simplified expression is:
\[
3 - 15i
\]
Therefore, the correct answer is:
**3 - 15i**