1.

If x `in` R then `(x^(2)+2x+a)/(x^(2)+4x+3a)` can take all real values ifA. `a in (0, 2)`B. `a in [0, 1]`C. `a in [-1, 1]`D. none of these

Answer» Correct Answer - B
Let `y = (x^(2)+2x + a)/(x^(2)+4x+3a)`. Then, `x^(2)(y-1)+2(2y-1) x + a(3y-1)=0`
`rArr" "4(2y-1)^(2) - 4(y-1) a (3y-1) ge 0` for all `y in R" "[because x in R]`
`rArr" "(4-3a)y^(2)-4(1-a)y+1 - a ge 0` for all y `in` R
`rArr" "4 - 3a gt 0` and Discriminant `le 0`
`rArr" "a lt (4)/(3) and 16 (1-a)^(2) - 4(1-a)(4-3a) le 0`
`rArr" "a lt (4)/(3) and a (a-1) le 0`
`rArr" "a lt (4)/(3) and 0 le a le 1 rArr 0 le a le 1 rArr a rArr [0, 1]`


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