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If x = 3 + i then x^3 - 3x^2 - 8x + 15 =

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If $x = 3 + i$ then $x^{3} - 3 x^{2} - 8 x + 15 =$

-18

-15

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Alexander Discussed

x = 3 + i

then

x^{3} - 3 x^{2} - 8 x + 15 =

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Text solutionVerified

x = 3 + i \Rightarrow x - 3 = i \Rightarrow (x - 3)^{2} = - 1

\Rightarrow x^{2} - 6 x + 10 = 0

∴ x^{3} - 3 x^{2} - 8 x + 15

= x (x^{2} - 6 x + 10) + 3 (x^{2} - 6 x + 10) - 15

= x (0) + 3 (0) - 15 = - 15.

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