Math Problem Statement

Write the following numbers in a + bi form: (a) (1 + 4i)^2 (b) i(π - 4i) (c) (-3 + 5i) / i

Solution

It looks like you're working on complex numbers in the form of a+bia + bi, and the answers for parts (a), (b), and (c) seem to have been partially evaluated.

Let’s go through them step by step to check what went wrong:

Part (a):
We are given (1+4i)2(1 + 4i)^2.

First, we expand: (1+4i)2=(1)2+2(1)(4i)+(4i)2(1 + 4i)^2 = (1)^2 + 2(1)(4i) + (4i)^2 =1+8i+16i2= 1 + 8i + 16i^2 Since i2=1i^2 = -1, we get: 1+8i16=15+8i1 + 8i - 16 = -15 + 8i So, the correct answer for part (a) is 15+8i-15 + 8i, which looks correct.

Part (b):
We are given i(π4i)i(\pi - 4i).

Distribute the ii: i(π4i)=iπ4i2i(\pi - 4i) = i\pi - 4i^2 Since i2=1i^2 = -1, we get: iπ+4=4+iπi\pi + 4 = 4 + i\pi So, the correct answer for part (b) is 4+πi4 + \pi i, which also seems correct.

Part (c):
We are given 3+5ii\frac{-3 + 5i}{i}.

We can multiply both the numerator and the denominator by ii to simplify: 3+5ii×ii=(3+5i)ii2\frac{-3 + 5i}{i} \times \frac{i}{i} = \frac{(-3 + 5i)i}{i^2} Since i2=1i^2 = -1, this simplifies to: 3i+5i21=3i51=3i+5\frac{-3i + 5i^2}{-1} = \frac{-3i - 5}{-1} = 3i + 5 Thus, the correct answer for part (c) is 5+3i5 + 3i, but your submission shows 3i-3i, which is incorrect.

Would you like more detailed steps or help with anything else related to complex numbers?


Here are five related questions to deepen your understanding:

  1. How do we handle the complex conjugate when dividing complex numbers?
  2. What does it mean for a complex number to be in the form a+bia + bi?
  3. How do you simplify powers of ii (e.g., i3i^3, i4i^4)?
  4. What is the geometric interpretation of multiplying two complex numbers?
  5. How can you check if the real and imaginary parts of your complex number calculations are correct?

Tip: To avoid errors when expanding or simplifying complex numbers, remember to always check for i2=1i^2 = -1 in your steps!

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Operations with Complex Numbers
Exponentiation
Multiplication and Division of Complex Numbers

Formulas

(a + bi)^2 = a^2 + 2abi + (bi)^2
i^2 = -1
i(π - 4i) = iπ - 4i^2
Dividing by i: multiply numerator and denominator by i

Theorems

Complex number multiplication and division
Imaginary unit properties

Suitable Grade Level

Grades 9-12