1.

If `.^(6)C_(k) + 2* .^(6)C_(k+1) + .^(6)C_(k+2) gt .^(8)C_(3)` then the quadratic equation whose roots are `alpha, beta and alpha^(k-1), beta^(k-1)` haveA. no common rootB. one common rootC. both common rootsD. imaginary roots

Answer» Correct Answer - C
We have, `.^(6)C_(k) + 2* .^(6)C_(k+1)+.^(6)C_(k+2) gt .^(8)C_(3)`
`rArr" "(.^(6)C_(k)+.^(6)C_(k+1))+(.^(6)C_(k+1)+ .^(6)C_(k+2)) gt .^(8)C_(3)`
`rArr" ".^(7)C_(k+1)+.^(7)C_(k+2) gt .^(8)C_(3)`
`rArr" ".^(8)C_(k+2) gt .^(8)C_(3) rArr k + 2 = 4" "[because .^(8)C_(4) gt .^(8)C_(3)]`
`rArr" "k = 2`
`therefore" "alpha^(k-1) = alpha and beta^(k-1) = beta`
Thus, the quadratic equations having roots `alpha and beta and alpha^(k-1) and beta^(k-1)` are identical.
Hence, they have both roots common.


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