Silvanus P. Thompson Text problem

Hi there,

I am a Physics teacher and for a bit of fun I am working through Calculus made easy by Thompson. I have got stuck on some algebra on q.7 exercise X. The question asks " Find the maxima and minima of y = 3x /(x^2 - 3) + 0.5x + 5.

So I have differentiated this and got (-3x^2 - 9)/(x^2-3)^2 + 5

I then equated the differential to zero and tried to solve for x. I got the equation down to 12x^2 + 9 = x^4 but now I am stuck.. How do I simplify this to get x? http://www.mathhelpforum.com/math-he...cons/icon5.gif