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The largest interval for which`x^(12)+x^9+x^4-x+1>0``-4A. `-4ltx le0`B. `0ltx lt1`C. `-100 lt x lt100`D. `-ooltxltoo` |
Answer» Correct Answer - D Given, `x^(12)-x^(9)+x^(4)-x+1gt0` here, three cases arises: Case I When `x le0impliesx^(12)gt0,-x^(9)gt0,x^(4)gt0,-xgt0` `thereforex^(12)-x^(9)+x^(4)-x+1 gt 0,AA x le0" "...(i)` Case II When `0 lt x le 1` `x^(9)lt x^(4)and x lt1implies-x^(9)+x^(4)gt0and a-xgt0` `thereforex^(12)-x^(9)+x^(4)-x+1gt0 ltx le1` Case III When `x gt 1 implies x^(12)gtx^(9)and x^(4)gtx` `thereforex^(12)-x^(9)+x^(4)-x+1gt0,AAxgt1" "...(iii)` From Eqs. (i), (ii), (iii), the above equation holds for all ` x in R.` |
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