Lesson Example Discussion Quiz: Class Homework |
Step-1 |
Title: Division of complex numbers |
Grade: 8-b Lesson: S2-L7 |
Explanation: Hello Students, time to practice and review the steps for the problem. |
Lesson Steps
Step | Type | Explanation | Answer |
---|---|---|---|
1 |
Problem |
Divide the complex number \$(2 - 3i)/(1 + 2i)\$ and express your answer in standard form. |
|
2 |
Step |
Given that |
\$(2 - 3i)/(1 + 2i)\$ |
3 |
Step |
Identify the conjugate of the denominator: |
The denominator is 1+2i, and its conjugate is 1−2i. |
4 |
Step |
Multiply the numerator and the denominator by the conjugate of the denominator: |
\$((2 - 3i)/(1 + 2i)) \times ((1 - 2i)/(1 - 2i))\$ |
5 |
Step |
Expand the numerator: Apply the distributive property (FOIL method): |
(2 - 3i)(1 - 2i) \$2 \times 1 + 2(-2i) + (-3i)1 + (-3i) \times (-2i)\$ \$2 - 4i - 3i + 6i^2\$ Since \$i^2 = -1\$: \$2 - 4i - 3i + 6(-1)\$ \$2 - 4i - 3i - 6\$ |
6 |
Step |
Combine like terms: |
(2 - 6) + (-4i - 3i) ⇒ -4 - 7i |
7 |
Step |
Expand the denominator: |
(1 + 2i)(1 - 2i) |
8 |
Hint |
Apply the difference of squares formula (a + bi)(a - bi) = a^2 - (bi)^2 : |
\$1^2 - (2i)^2\$ 5 |
9 |
Step |
Combine the results: |
\$(-4 - 7i)/5\$ |
10 |
Step |
Separate the real and imaginary parts: |
\$(-4/5) + (-7i/5)\$ ⇒ -0.8 - 1.4i |
11 |
Step |
Therefore the division of \$(2 - 3i)/(1 + 2i)\$ is -0.8 - 1.4i. |
|
12 |
Choice.A |
This option represents the result we calculated. It shows that when you divide 2 - 3i by 1 + 2i, you get -0.8 - 1.4i, which is the correct answer |
-0.8 - 1.4i |
13 |
Choice.B |
This option is incorrect. It has the wrong signs for both the real and imaginary parts. It suggests that the result is positive, but our calculation resulted in a negative value |
0.8 + 1.4i |
14 |
Choice.C |
This option is incorrect. While the signs are correct compared to option B, the values are inaccurate. The real part should be negative and the imaginary part should be -1.4i, not positive |
0.8 + 1.6i |
15 |
Choice.D |
This option is incorrect. It has the wrong signs and values. The real part should be negative and the imaginary part should be -1.4i, not positive |
0.8 - 1.6i |
16 |
Answer |
Option |
A |
17 |
Sumup |
Can you summarize what you’ve understood in the above steps? |
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