lua获取文件修改时间:(xy+1)(x+1)(y+1)+xy

(xy+1)(x+1)(y+1)+xy 因式分解xy-x-y+1 因式分解（x+y)*(x+y+2xy)+(xy+1)*(xy-1) [（xy+2)(xy-4)-(2xy)²+8]÷xy 其中x=1/8 y=-3. (x+y-2xy)(x+y-2)+(xy-1)^2分解因式 分解因式：(x+y-2xy)(x+y-2)+(xy-1)^2 分解因式（xy-1）^2+(x+y-2)(x+y-2xy) x, y>0。求证x/y+y/x+xy>x+y+1 已知x-y=11求(xy-1)的平方＋(x+y-2)×(x+y-2xy)的值 因式分解(1-X^2)(1-Y^2)-4XY