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A Complex Equation (Posted on 2023-04-28) Difficulty: 2 of 5
Solve:

2x-x^3 = 3i

No Solution Yet Submitted by Ady TZIDON    
Rating: 4.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re: Puzzle Solution | Comment 3 of 4 |
(In reply to Puzzle Solution by K Sengupta)

Both Matlab and Wolfram Alpha have a negative sign on the imaginary part of the complex solutions:


Matlab:
>> syms x
>> eq = 2*x-x^3 == 3i
eq =
- x^3 + 2*x == 3i
>> sx=solve(eq,x)
sx =
                 1i
- 11^(1/2)/2 - 1i/2
  11^(1/2)/2 - 1i/2
  
making the three solutions

x = i
x = -sqrt(11)/2 - i/2
x = sqrt(11)/2 - i/2

and

Wolfram Alpha:
x = i
x = 1/2 (-sqrt(11) + -i)
x = 1/2 (sqrt(11) + -i)

Wolfram Alpha also provides further clarification:

(2x-x^3 - 3i) / (x-i)  = -(x^2 + i x - 3) = -x^2 - i x + 3

Edited on April 28, 2023, 3:45 pm
  Posted by Charlie on 2023-04-28 14:18:21

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