a maths question

Let y=2x+5/x^2+6.Find the range of values of y for all real values of x.Hence,find the range of values of |y|.

By rearrangement ,

xy^2+6y = 2x+5

x^2y -2x+(6y-5) = 0

as x is real , D=>0

4 - (y)(6y-5) => 0

6y^2 -5y -4 <=0

-1/2<= y <=4/3

|y| = | 2x+5/x^2+6 | = 0<=y<= 4/3 or -1/2<= y <0

2007-12-08 21:06:12 補充：
therefore , ramge of |y| is 0

2007-12-08 21:07:46 補充：
ramge of |y| is 少於4/3 |y| 大於0

are u crazy ??