1.

If the equation x^4-λx^2+9=0 has four real and distinct roots, then `lamda` lies in the intervalA. `(-oo,-6)uu(6,oo)`B. `(0,oo)`C. `(6,oo)`D. `(-oo,-6)`

Answer» Correct Answer - C
`x^(4)-lamdax^(2)+9=0`
Let `x^(2)=tge0`
`:.f(t)=t^(2)-lamdat+9=0" "(1)`
If given equation has four real and distinct roods, then both roots of (1) must be positive
`:.Dgt0implieslamda^(2)-36gt0" "(2)`
`(-b)/(2a)gt0implies(lamda)/(2)gt0orlamdagt0" "(3)`
`f(0)gtor9gt0" "(4)`
`:.lambda in(-6,oo)" "["from(2),(3),(4)"]`.


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