*3.3（代数：求解2 * 2线性方程）可以使用编程练习题1.13中给出的Cramer规则解线性方程组：
编写程序，提示用户输入a, b, c, d, e 和 f，然后显示结果。如果 ad - bc为0，则报告消息 “The equation has no solution”（方程式无解）。 这里有些运行示例：
Here are some simple runs:
Enter a, b, c, d, e, f:9.0 4.0 3.0 -5.0 -6.0 -21.0
x is -2.0 and y is 3.0
Enter a, b, c, d, e, f:1.0 2.0 2.0 4.0 4.0 5.0
The equation has no solution
*3.3(Algebra: solve 2 * 2 linear equations) A linear equation can be solved using Cramer’s rule given in Programming Exercise 1.13. Write a program that prompts the user to enter a, b, c, d, e and f and displays the result. If ad - bc is 0, report that “The equation has no solution.” Here are some simple runs:
Enter a, b, c, d, e, f:9.0 4.0 3.0 -5.0 -6.0 -21.0
x is -2.0 and y is 3.0
Enter a, b, c, d, e, f:1.0 2.0 2.0 4.0 4.0 5.0
The equation has no solution
参考代码：
package chapter03; import java.util.Scanner; public class Code_03 { public static void main(String[] args){ Scanner input = new Scanner(System.in); System.out.print("Enter a,b,c,d,e,f: "); double a = input.nextDouble(); double b = input.nextDouble(); double c = input.nextDouble(); double d = input.nextDouble(); double e = input.nextDouble(); double f = input.nextDouble(); double medius = a * d - b * c; if (medius == 0){ System.out.println("The eqution has no solution"); } else{ double x = (e * d - b * f) / medius; double y = (a * f - e * c) / medius; System.out.println("x is " + x + " and y is " + y); } } } 结果显示： Enter a,b,c,d,e,f: 1.0 2.0 2.0 4.0 4.0 5.0 The eqution has no solution Process finished with exit code 0