X2y2-x2-y2+1 =x2(y2-1)-(y2-1) =(y2-1)(x2-1) =(y+1)(y-1)(x+1)(x-1) 中的=x2(y2-1)-(y2-1) =(y2-1)(x2-1是怎么算出来的?

因式分解x2y2-x2-y2+1 X2y2-x2-y2+1因式分解. x2+y2-x2y2-4xy-1 X2y2-x2-y2+1 =x2(y2-1)-(y2-1) =(y2-1)(x2-1) =(y+1)(y-1)(x+1)(x-1) 中的=x2(y2-1)-(y2-1) =(y2-1)(x2-1是怎么算出来的? 已知x2+4y2+x2y2+1=6xy,则(x4-y4)/(2x2+xy-y2)*(2x-y)/(xy-y2)/(x2+y2/y)2= (x2+y2)(x2-xy+y2)-2x2y2因式分解 x2y2-x2-y2+4xy+1分解因式 (x2+y2-1)-4x2y2因式分解2是平方 (x2+y2)2-4x2y2 因式分解 因式分解(x2+y2-a2)2-4x2y2 4x2y2-(x2+y2)2的答案 求极限lim(x,y)→(0,0) [1-cos(x2+y2)]/[(x2+y2)e^x2y2] 化简求值（2X2-2y2）-3（X2y2+X2）+3（X2y2+y2）,其中X=-1,y=2 （2x2-2y2）-3（x2y2+x2）+3x2y2+y2.提示：x=-1,y=2 化简求值 lim(x,y)→(0,0)(1-cos(x2+y2))/(x2+y2)x2lim(x,y)→(0,0)(1-cos(x2+y2))/(x2+y2)x2y2 已知x.y为正整数,且满足2x2+3y2=4x2y2+1,求x2+y2的值过程 已知:x-y= -2 求(x2+y2)2-4xy(x2+y2)+4x2y2的值 因式分解,x4-7x2y2+y4=?x4-7x2y2+y4=?应该是(x2+?xy+y2)(x2-?xy+y2) 的形式,那个?是多少