1.

Given that, for all real x, the expression `(x^2+2x+4)/(x^2-2x+4)` lies between `1/3` and 3. The values between which the expression `(9.3^(2x)+6.3^x+4)/(9.3^(2x)-6.3^x+4)` lies areA. `3^(-1) and 3`B. `-2 and 0`C. `-1 and 1`D. 0 and 2

Answer» Correct Answer - A
It is given that `(1)/(3) lt (x^(2)-2x+4)/(x^(2)+2x+4) lt 3` for all x `in` R.
`rArr" "(1)/(3) lt (x^(2)+2x+4)/(x^(2)-2x+4) lt 3` for all x `in R" "...(i)`
Let `3^(x+1) = y`. Then, `y in R` for all x `in` R.
Also,
`(9*3^(2x)+6*3^(x)+4)/(9*3^(2x)-6*3^(x)+4)=(3^(2x+2)+2*3^(x+1)+4)/(3^(2x+2)-2*3^(x+1)+4)=(y^(2)+2y+4)/(y^(2)-2y+4)`
But, `(1)/(3) lt (y^(2)+2y+4)/(y^(2)-2y+4) lt 3" "["From (i)"]`
`therefore" "(1)/(3) lt (9*3^(2x)+6*3^(x)+4)/(9*3^(2x)-6*3^(x)+4) lt 3`


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