1.

If `cos^2x-(c-1)cosx+2cgeq6`for every `x in R ,`then the true set of values of `c`is`(2,oo)`(b) `(4,oo)`(c) `(-oo,-2)`(d) `(-oo,-4)`

Answer» `cos^2x-(c-1)x + 2c ge 6`
`=>cos^2x-(c-1)cosx+2c-6 ge 0`
`=>cos^2x-(c-3)cosx - 2cosx+(2c-6) ge 0`
`=>cosx(cosx-(c-3))-2(cosx-(c-3)) ge 0`
`=>(cosx-(c-3))(cosx-2) ge 0`
As, `cosx - 2` can not be greater than or equal to `2`.
`:. cosx le c-3`
`=>1 le c-3`
`=>4 le c`
`:. c in [4,oo).`


Discussion

No Comment Found

Related InterviewSolutions