Let y in the form of a + ib, where a and b are real numbers, be the cubic roots of a complex number z 20, where z =2 4+i3. Find

Question

2 years ago

7

a + b.

1 answer:

GalinKa [24] · Answer 1 · 2023-06-19T05:13:20+03:00

The possible values of a + b are 0.89, 3.01 and -3.9

<h3>How to determine the value of a + b?</h3>

The given parameters are:

y = a + ib

z = 24 + i3

Where:

y = ∛z

Take the cube of both sides

y³ = z

Substitute the values for y and z

(a + ib)³ = 24 + i3

Expand

a³ + 3a²(ib) + 3a(ib)² + (ib)³ = 24 + i3

Further, expand

a³ + i3a²b + i²3ab² + i³b³ = 24 + i3

In complex numbers;

i² = -1 and i³= -i

So, we have:

a³ + i3a²b + (-1)3ab² -ib³ = 24 + i3

Further expand

a³ + i3a²b - 3ab² - ib³ = 24 + i3

By comparing both sides of the equation, we have:

a³ - 3ab² = 24

i3a²b - ib³ = i3

Divide through by i

3a²b - b³ = 3

So, we have:

a³ - 3ab² = 24

3a²b - b³ = 3

Using a graphing tool, we have:

(a,b) = (-1.55, 2.44), (2.89,0.12) and (-1.34,-2.56)

Add these values

a + b = 0.89, 3.01 and -3.9

Hence, the possible values of a + b are 0.89, 3.01 and -3.9