利用c++封装，实现了多项式加法 减法 乘法 求值 求导 求积分 判断是否相等等操作， 而且使用了文件操作，进行文件的读取。异常处理较好，程序健壮性不错(The use of C + + package, to achieve a polynomial addition and subtraction multiplication and multiplication of the demand-seeking derivative to determine whether the same judge, and the use of the file operation, the file is read. Exception handling is good, the program robustness good)