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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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Answer» 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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