y = 0.5 - x - sqrt(0.25 - x)
Can I simplify this equation, making it look like a product times itself?
What are you asking? Can you put this in the form $\displaystyle (a + b)^2$? It's possible, but the forms for a and b are likely to be infinite series.
I know of no way to simplify this expression. (If it were $\displaystyle (0.5 - x) - \sqrt{0.5 - x}$, then you can do some factoring.)
-Dan