(x-y)(2x-2y-3)-2为啥 =2（x-y)(x-y)-3(x-y)-2 后得到 =(2x-2y+1)(x-y-2)

(x-y)(2x-2y-3)-2为啥 =2（x-y)(x-y)-3(x-y)-2 后得到 =(2x-2y+1)(x-y-2) 方程y-6y'+9y=x^2e^3x的特解应设为什么?为啥是y*=x^2(ax^2+bx+c)e^3x x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 lingo中min=sqrt(x^2+(y-a)^2)+sqrt((x-b)^2+(y-c)^2)+y;为啥不对 X²-XY-6Y²+2X-Y+1先配二次项=(x-3y)(x+2y)+2x-y+1需要x-3y 所以构造x-3y=(x-3y)(x+2y)+x-3y+x+2y+1=(x-3y)(x+2y+1)+x+2y+1=(x-3y+1)(x-2y+1)其中说的先配二次项为啥要配?二次项怎么配还有说的需要X-3Y所以构造x-3y (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= (x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) (x+y)(2x-3y)=? 函数我苯~请问:x,y满足X+2Y小于=4 X-Y小于=1 X+2大于=0 目标函数Z=3X-Y最大值是5?为啥 怎么求呢? y=ln(x+2)的导数为啥不是等于1/(x+2), y=根号下x-2+根号下1-x是函数吗为啥 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 已知x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² x(x-y)2-(y-x)3 #include main() { int x=2,y=3; x%=y+3; printf(%d,x); } 谁能给解释一下输出值为啥等于2 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值