Step-1

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

Discussion: Step1 Step2 Step3 Step4 Step5

Step Type Explanation Answer

1

Problem

Compute the product of the complex numbers (2 + 3i) and (4 − i). What is the result in standard form?

2

Step

Write down the expression:

\$(2 + 3i) \times (4 - i)\$

3

Hint

Apply the distributive property (FOIL method) to expand the product:

\$(2 \times 4) + (2 \times (−i)) + (3i \times 4) + (3i \times (−i))\$

4

Step

Perform each multiplication:
Multiply the real parts:

\$2 \times 4 = 8\$

5

Step

Multiply the real part of the first number by the imaginary part of the second number:

\$2 \times (-i) = -2i\$

6

Step

Multiply the imaginary part of the first number by the real part of the second number:

\$3i \times 4 = 12i\$

7

Step

Multiply the imaginary parts:

\$3i \times (-i) = -3i^2\$

Recall that \$i^2 = -1\$, so:

\$-3i^2 = -3(-1) = 3\$

8

Step

Combine all the results:

\$8 - 2i + 12i + 3\$

9

Step

Combine the real and imaginary parts:

11 + 10i

10

Step

TThe result of the product of (2+3i) and (4−i) in standard form is 11+10i.

11

Choice.A

This option represents a complex number with a positive real part and a negative imaginary part that does not match the result of our computation

10 - 11i

12

Choice.B

This option represents a complex number with a negative real part and a negative imaginary part, which is not consistent with our computed result

-11 - 10i

13

Choice.C

This option shows a complex number with a negative real part and a positive imaginary part, which does not correspond to our answer

-10 + 5i

14

Choice.D

This option matches our computed result, which correctly combines the real part 11 and the imaginary part 10i

11 + 10i

15

Answer

Option

D

16

Sumup

Can you summarize what you’ve understood in the above steps?

Discussion: Step1 Step2 Step3 Step4 Step5


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