1.

the determinant `|{:(a,,b,,aalpha+b),(b,,c,,balpha+c),(aalpha+b,,balpha+c,,0):}|=0` is equal to zero ifA. a,b,c are in A.PB. a,b,c are in G.P.C. `alpha` is a root of the equation `ax^(2) +bx+c=0`D. `(x-alpha)` is a factor fo `ax^(2) +2bx+c`

Answer» Correct Answer - B::D
Given that `|{:(a,,b,,aalpha+b),(b,,c,,balpha+c),(aalpha+b,,balpha+c,,0):}|=0`
Operating `C_(3) to C_(3) -C_(1) alpha-C_(2)` we get
`|{:(a,,b,,0),(b,,c,,0),(aalpha+b,,balpha+c,,-(aalpha^(2)+balpha+balpha+c)):}|=0`
`rArr (aalpha^(2) +2balpha +c) |{:(a,,b,,0),(b,,c,,0),(aalpha +b,,balpha+c,,1):}|=0`
`rArr (ac-b^(2)) (aalpha^(2) +2balpha+c)=0`
so , either `ac-b^(2)=0 " or " aalpha^(2) +2balpha +c=0`
This means that either a,b,c are in G.P. or `(x-alpha)` is a factor of `ax^(2) +2bx +C`


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