Lesson Example Discussion Quiz: Class Homework |
Step-4 |
Title: Multiplication of complex numbers |
Grade: 8-b Lesson: S2-L6 |
Explanation: Hello Students, time to practice and review the steps for the problem. |
Lesson Steps
Step | Type | Explanation | Answer |
---|---|---|---|
1 |
Problem |
Multiply the following complex numbers ( -16 + 2i) and ( 8 - 8i). |
|
2 |
Step |
The given expression |
( -16 + 2i) and ( 8 - 8i) |
3 |
Hint |
Apply the distributive property (FOIL method): |
\$- 16 times 8 - 16 times ( - 8i) + 2i times 8 + 2i times (-8i)\$ |
4 |
Step |
Calculate each term: |
\$- 128 + 128i + 16i - 16i^2\$ |
5 |
Hint |
Since \$i^2 = - 1\$. |
|
6 |
Step |
Plug the \$i^2 = - 1\$ in the above expression and then simplify it: |
\$ - 128 + 144i - 16 times (-1)\$ ⇒ - 128 + 144i + 16 ⇒ - 112 + 144i |
7 |
Step |
Therefore the multiply of complex numbers is - 112 + 144i. |
|
8 |
Choice.A |
This result does not match our calculation because the signs of the real parts are incorrect. In the correct solution, the real part is −112, not 112 |
112 + 144i |
9 |
Choice.B |
Wrong: Because the real part of the product is - 112 (not 121), and the imaginary part is 144i (not - 144i) |
121 - 144i |
10 |
Choice.C |
The calculation of complex numbers confirms the accuracy of this option, making it the correct choice |
-112 + 144i i |
11 |
Choice.D |
The real part should be −112, not −121. So, this is option is wrong |
-121 + 144i |
12 |
Answer |
Option |
C |
13 |
Sumup |
Can you summarize what you’ve understood in the above steps? |
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