－x²－4y²＋4xy. 3y³－18y²＋27y. ﹙m＋n﹚²－4m ﹙m＋n﹚＋4m²

显示全部楼层 · 2012-11-15 18:42:34

－x2－4y2＋4xy. =-(x-2y)2 3y3－18y2＋27y. =3y(y2-6y+9)=3y(y-3)2 ﹙m＋n﹚2－4m ﹙m＋n﹚＋4m2=(m+n-2m)2=(n-m)2 4xy2－4x2y－y3. =-y(4x2 -4xy+y2) =-y(2x-y)2 ﹙x2－2x﹚2＋2﹙x2－2x﹚＋1.
=(x2-2x+1)2=(x-1)&#830...

千问 · 2012-11-15 18:42:34

－x2－4y2＋4xy.=-(x2-4xy+4y2)=-(x+2y)2 ﹙m＋n﹚2－4m ﹙m＋n﹚＋4m2=[(m+n)-2m]2=(n-m)2 4xy2－4x2y－y3=-y(4x2-4x...