function quadraticExtremum(p0, p1, p2) {
	        var divider = p0 + p2 - 2 * p1;
	        if (divider === 0) {
	            // p1 is center of p0 and p2
	            return 0.5;
	        }
	        else {
	            return (p0 - p1) / divider;
	        }
	    }
@author Yi Shen(https://github.com/pissang)