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The equation ` cos^8 x + b cos^4 x + 1 = 0` will have a solution if b belongs to :

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The equation ` cos^8 x + b cos^4 x + 1 = 0` will have a solution if b belongs to :
A. `(-oo, 2]`
B. `[2, oo)`
C. `(-oo, -2]`
D. none of these
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1 Answer

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Correct Answer - C
`cos^(8)x+b cos^(4) x+1=0`
`rArr b=-(cos^(4) x+1/(cos^(4) x)) le -2 AA x in R`
`rArr b in (-oo, -2]`
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