[编程入门]自定义函数求一元二次方程-题解（Java代码）

解题思路:

注意事项:

参考代码:

import java.util.Scanner;

public class Main {

// 大于零

public static void fun1(double a,double b,double c)

{

double x1,x2;

double z=b*b-4*a*c;

x1=((-b)+Math.sqrt(z))/(2*a);

x2=((-b)-Math.sqrt(z))/(2*a);

System.out.print(String.format("x1=%.3f x2=%.3f", x1,x2));

}

// 等于零

public static void fun2(double a,double b,double c)

{

double x1,x2;

double z=b*b-4*a*c;

x1=(-b)/(2*a);

x2=(-b)/(2*a);

System.out.print(String.format("x1=%.3f x2=%.3f", x1,x2));

}

// 小于零

public static void fun3(double a,double b,double c)

{

double x1,x2;

double z=4*a*c-b*b;

x1=-b/(2*a);

x2=-b/(2*a);

System.out.print(String.format("x1=%.3f+%.3fi",x1,Math.sqrt(z)/(2*a)));

System.out.print(" ");

System.out.print(String.format("x2=%.3f-%.3fi",x2,Math.sqrt(z)/(2*a)));

}

public static void main(String[] args) 

{

Scanner in = new Scanner(System.in);

double a = in.nextDouble();

double b = in.nextDouble();

double c = in.nextDouble();

double x1 = 0,x2 = 0;

double z=b*b-4*a*c;

if(z>0)

{

fun1(a,b,c);

}

else if(z==0)

{

fun2(a,b,c);

}

else

{

fun3(a,b,c);

}

}

}