Question

please solve this problem

Answer 1

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Here's your answer...

In the above equation, let x² = y
Then the equation becomes y²-8y+9=0
(y-9)(y+1)=0
y = 9 or -1
x² = 9 or -1
x = ±3 or ±i

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Answer 2

x⁴ - 8x² - 9 = 0

Factorise:

(x² + 1)(x² - 9) = 0

Factorise again:

(x² + 1)(x + 3) ( x - 3) = 0

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When (x² + 1) = 0

x² + 1 = 0

x² = -1

x = ± 1i (no real roots)

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When (x + 3) = 0

x + 3 = 0

x = - 3

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When (x - 3) = 0

x -3 = 0

x = 3

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Answer: The roots are 1i, -1i, -3 and 3

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