1-2的相反数是2-1．
故填空答案是2-1．
解方程：
（1）x2-x-3=0
（2）（x+3）2=2（x+3）
The addition problem above shows four of the 24 different integers that can be formed by using each of the digits 1, 2, 3 and 4 exactly once in each integer. What is the sum of these 24 integers ？（）
