m（x2-2xy+5y2）-n（4x2-xy-y2）怎样化简拜托各位了 3Q

m（x2-2xy+5y2）-n（4x2-xy-y2）怎样化简拜托各位了 3Q 4x2-3y2+2xy-4x2+5x2 (x2+xy+y2)-4xy(x2+y2) 计算(x+y/x-y + 4xy/y2-x2)(x2-9y2)/（x2+2xy-3y2） 多项式x2+xy+y2=m,x2-xy+y2=n,则x2+y2用m,n表示为A.m+n B.m-n C.m+n/2 D.m-n/2 (2x2-3xy+4y2)+(x2+2xy-3y2）化简（要有过程） 4x2-y2/x2-2xy+y2 +(2x-y)/2x2-2xy x2+y2+2xy=256 x2+y2-2xy=4 (x2, 已知x2+y2+4x-2y+5=0,求x2+2xy+y2值 求助数学解答题.关于因式分解（a+b）2(a-b)+（a-b）2（a+b）（x+y）2-4y2（m+2n）2+2(m+2n)(2m+n)+(2m+n)2x2+2xy+y2-4x-4y-5a4-a2-72x2-3x3-9+27x 已知x2+y2=7,xy=-2,求5x2—3xy—4y2—11xy—7x2+2y2的值 若3x2-4xy+y2=-3,2x2+3xy-2y2=8,求5x2-18xy+7y2的值. 5x2-3xy-4y2-11xy+(-7x2)-(-2y2),其中x2+y2=7,xy=-2,求值 已知X2+y2=7,Xy=-2,求多项式5X2一3Xy-4y2-11Xy-7X2+2y2的值. 已知x2+y2 =7,xy=-2.求5x2 -3xy-4y2 -11xy-7x2 +2y2 2(x-xy)-3(2x2-3xy）2[x2（2x2-xy+y2)] x2-2xy+y2-4分解因式 4x2+3xy-2y2因式分解