Question

1. If x = 3 + i, then x3 - 3x2 - 8x + 15 =​

Answer 1

Answer:

$\sf ({3x + i})^{2} + 8(3x + i) + 15 =$

$\sf{3x + i}^{2} = {3x}^{2} + 2(3x \times i) + {i}^{2}$

$\sf \to9 {x}^{2} + 2(3xi) + {i}^{2}$

$\sf \to {9x}^{2} + 6xi + {i}^{2}$

$\sf \: 8x$

$\sf \to8x = 8 \times (3x + i)$

$\sf \to24x + 8i$

$\sf \underline{let \: us \: solve \ \: : }$

$\sf {9x}^{2} + 6xi + {i}^{2} + 24x + 8i + 15$

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