The roots of the equation x4-8 x2-9-0 areA- - 3- - 1B- - 3- - iC- - 2- - iD- 3 i - 2

The correct option is B Equation nbsp;x^4 8x^2 9 = 0 ⇒ x^4 9x^2+x^2 9 = 0 ⇒ nbsp;x^2(x^2 9)+1(x^2 9) = 0 ⇒ (x^2+1)(x^2 9) = 0 nbsp;⇒ x = nbsp;±i, n ...

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Standard XII

Mathematics

Roots of a Quadratic Equation

The roots of ...

Question

The roots of the equation $x^{4} - 8 x^{2} - 9$ = 0 are

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3i , 2

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Solution

The correct option is B

Equation $x^{4} - 8 x^{2} - 9$ = 0

⇒ $x^{4} - 9 x^{2} + x^{2} - 9$ = 0 ⇒ $x^{2} (x^{2} - 9) + 1 (x^{2} - 9)$ = 0

⇒ $(x^{2} + 1) (x^{2} - 9)$ = 0 ⇒ $x$ = ± $i$ , ±3

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The roots of the equation x4−8x2−9 = 0 are

The correct option is B Equation x4−8x2−9 = 0 ⇒ x4−9x2+x2−9 = 0 ⇒ x2(x2−9)+1(x2−9) = 0 ⇒ (x2+1)(x2−9) = 0 ⇒ x = ±i, ±3

The roots of the equation $x^{4} - 8 x^{2} - 9$ = 0 are

The correct option is B

Equation $x^{4} - 8 x^{2} - 9$ = 0

⇒ $x^{4} - 9 x^{2} + x^{2} - 9$ = 0 ⇒ $x^{2} (x^{2} - 9) + 1 (x^{2} - 9)$ = 0

⇒ $(x^{2} + 1) (x^{2} - 9)$ = 0 ⇒ $x$ = ± $i$ , ±3