Numerical Methods

quadratic equation

by joe chan

JavaScript

function solve (a,b,c) {
	var x1, x2;
    var d = b*b-4*a*c;
    if (d >= 0) {
        var sd = Math.sqrt(d);
        x1 = (-b+sd)/2/a;
        x2 = (-b-sd)/2/a;

        return [x1,x2];
    } else { 
       
        return [];
    }
}
//  (p1-p2)*y+(q2-q1)*x-p1*q2+p2*q1 = 0




function slovePoint(a1,b1,c1,a2,b2,c2){
		var x,y;
    x=(b2*c1-b1*c2)/(a2*b1-a1*b2);
    y=-(a2*c1-a1*c2)/(a2*b1-a1*b2);
    
    return [x,y]
}
//	x=(b2*c1-b1*c2)/(a2*b1-a1*b2),y=-(a2*c1-a1*c2)/(a2*b1-a1*b2)



var roots = solve (1,2,-3);
//console.log (roots);
if (roots.length === 0)
    console.log ('no real roots');
else 
    console.log ('x1: ' + roots[0] + '; ' + 
                 'x2: ' + roots[1]);

var point = slovePoint(1,0,1,1,1,-2) ;
// x=-1  ; x+y = 2  x=-1 y=3
console.log(point);