public ComplexClass Subtract(ComplexClass other)
 {
     return(new ComplexClass(
                this.a - other.a,
                this.b - other.b
                ));
 }
 public ComplexClass Multiply(ComplexClass other)
 {
     return(new ComplexClass(
                this.a * other.a - this.b * other.b,
                this.a * other.b - this.b * other.a
                ));
 }
 public ComplexClass Add(ComplexClass other)
 {
     return(new ComplexClass(
                other.a + this.a,
                other.b + this.b
                ));
 }