
Range of Y question
Hello, I wonder if anyone can help me, would be very grateful if anyone could.
If you wanted to find the range of a curve say y=(2x^2
+ 5x+3)/(4x^2 + 5x +3) instead of using calculus to find the stationary points and then subing back in to find e.g. the min. value of y or whatever, you can rearrange :
(4y2)x^2 + (5y5)x + 3y3 =0 and then using b^2  4ac>0 to find the possible range...
just wondered...when does this method fail? It failed when I tried to use it for some other questions like y=[(x1)(3x+2)]/[(x+1)^2] and pretty certain I didn't make any algebraic slip ups there.
Anyways, thanks
Jess x