Question

If G and L are the greatest and least values of the expression`(2x^(2)-3x+2)/(2x^(2)+3x+2), x epsilonR` respectively.
G and L are the roots of the equation
A. `5x^(2)-26x+5=0`
B. `7x^(2)-50x+7=0`
C. `9x^(2)-82x+9=0`
D. `11x^(2)-122x+11=0`

Answer 1

Correct Answer - B
Let `y=(2x^(2)-3x+2)/(2x^(2)+3x+2)`
`implies2x^(2)y+3xy+2y=2x^(2)-3x+2`
`implies2(y-1)x^(2)+3(y+1)x+2(y-1)=0`
As `x epsilonR`
`:.Dge0`
`=9(y+1)^(2)-4.2(y-1).2(y-1)ge0`
`implies9(y+1)^(2)-16(y-1)^(2)ge0`
`implies(3y+3)^(2)-(4y-4)^(2)ge0`
`implies(7y-1)(7-y)ge0`
`implies(7y-1)(y-7)le0`
`:.1/7leyle7`
`:.G=7` and `L=1/7`
`:.GL=1`
NOw `(G^(100)+L^(100))/2ge(GL)^(100)implies(G^(100)+L^(100))/2ge1`
`impliesG^(100)+L^(100)ge2`
The quadratic equation having roots G and L is
`x^(2)-(G+L)x+GL=0`
`impliesx^(2)-50/7x+1=0`
`implies7x^(2)-50x+7=0`