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If the equation x^4 -λx^2 +9 has only two real roods, then the set of values of `λ` isA. `(-oo,-6)`B. `(-6,6)`C. `{6}`D. `phi` |
Answer» Correct Answer - D From above discussion we have for `lamdain(-oo,6)uu(6,oo)` equation has either four distinct real or no real roots. For `lamda=6`, both roots are `pmsqrt3` Alternate method: `x^(4)-lamdax^(2)+9=0` or `x^(2)+(9)/(x^(2))=lamda` Now `(x-(3)/(x))^(2)=lamda-6` For above equation (i) four distinct real roots if `lamda-6gt0orlamdagt6`. (ii) no real roots if `lamda-6lt0orlamdalt6` (iii) real and equal repeating roots if `lamda=6` |
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