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Answer the following: Find the value of x4 + 9x3 + 35x2 − x + 164, if x = −5 + 4i

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Question

Answer the following:

Find the value of x4 + 9x3 + 35x2 − x + 164, if x = −5 + 4i

Sum
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Solution

x = − 5 + 4i

∴ x + 5 = 4i

∴ (x + 5)2 = 16i2

∴ x2 + 10x + 25 = − 16    ...[∵ i2 = − 1]

∴ x2 + 10x + 41 = 0   ...(i)

                              x2 − x + 4
∵ `x^2 + 10x + 41")"overline(x^4 + 9x^3 + 35x^2 - x + 164`
                              x4 + 10x3 + 41x2
                           −     −         −                             
                                  − x3 − 6x2 −      x + 164
                                 − x3 − 10x2 − 41x
                                 +     +         +                      
                                               4x2 + 40x + 164
                                               4x2 + 40x + 164
                                            −       −       −          
                                                                     0

∴ x4 + 9x3 + 35x2 − x + 164

= (x2 + 10x + 41) (x2 − x + 4)

= 0(x2 − x + 4)      ...[From (i)]

∴ x4 + 9x3 + 35x2 − x + 164 = 0

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Chapter 1: Complex Numbers - Miscellaneous Exercise 1.2 [Page 22]

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Balbharati Mathematics and Statistics (Arts and Science) Part 2 [English] Standard 11 Maharashtra State Board
Chapter 1 Complex Numbers
Miscellaneous Exercise 1.2 | Q II. (4) (ii) | Page 22

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