中四 A.maths - Inequalities2

y = ( x^2 + 6 ) / (2x-1) .

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

x=[2y+ √(4y^2-4y-24)]/2 OR x=[2y-√(4y^2-4y-24)]/2

So we have (4y^2-4y-24)＞＝ 0

y^2-y-6＞＝ 0
(y-3)(y+ 2)＞＝ 0
y＜＝-2 or y＞＝ 3

the range of values of y for all real values of x　other than 1/2 is
(-infinity,-2] and [3,infinity)

2008-05-12 16:49:40 補充：
最後個幾隻字只不過說明x不可以等於1/2﹐因為這時分母等於0﹐不合理。計y個range可以不用理會