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Question

Question: If ƒ(*x*) = *x*<sup>4</sup> + 9*x*<sup>3</sup> + 35*x*<sup>2</sup> – *x* + 4, then ƒ (– 5 + 2 \(\sqr...

If ƒ(x) = x4 + 9x3 + 35x2x + 4, then ƒ (– 5 + 2 4\sqrt{- 4}) is equal to –

A

– 160

B

160

C

0

D

None of thes

Answer

– 160

Explanation

Solution

Let, y = – 5 + 4i ⇒ y2 + 10y + 41 = 0

∴ ƒx) = x4 + 9x3 + 35x2 – x + 4

= x2 (x2 + 10x + 41) – x(x2 + 10x + 41) + 4(x2 + 10x + 41) – 160

= – 160

∴ ƒ (– 5 + 4i) = – 160