"求解一元二次方程ax^2+bx+c=0,公式：[−b±√(b^2−4ac)]/2a​"

public class Main{

public static void main(String[]args){

double a=1.0;double b=3.0;double c=-4.0;

//求平方根Math.sqrt()

double r1=(-b+Math.sqrt(b*b-4*a*c))/(2*a);

double r2=(-b-Math.sqrt(b*b-4*a*c))/(2*a);

System.out.println(r1+","+r2);

System.out.println(r1==1&&r2==-4?"测试通过":"测试失败");

}

}