4-1.Complex numbers
easy

यदि $x = 3 + i$ हो, तो $x^3 - 3x^2 - 8x + 15 = $

A

$6$

B

$10$

C

$-18$

D

$-15$

Solution

(d)$x = 3 + i\, \Rightarrow \,\,x – 3 = i\,$
$ \Rightarrow $ $\,x^2 – 6x + 10 = 0$ ==> $x^3 – 3x^2 – 8x + 15$
$ = x(x^2 – 6x + 10) + 3\,(x^2 – 6x + 10) – 15$
$ = x(0) + 3(0) – 15 = – 15$.

Standard 11
Mathematics

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