1.-2b
2.
3.=1/11(a-b)(121-a^2-ab-b^2)
4.=-2/3a(x^2-6x+9)
=-2/3(x-3)^2
5.=125x1.42-125x8.62
=125x(-7.2)
=-125x4x1.8
=-900
6.=x^2-2x+1+4x^2-4+4x^2+8x+4
=9x^2+6x+1
=(3x+1)^2
当x=1时,原式值为16
7.=-(x-y)^2+1
=(1-x+y)(1+x-y)
(1)-4ab
(2)第二个没有看明白
(3)将(b-a)立方=(b-a)*(a平方+a*b+b平方)代入,提取公因式即可.
(4)先提出:-2/3a,括号裏剩下(x平方-6*x+9)=(x-3)平方
(5)1.25×142-125×8.62=125×1.42-125×8.62=125×(1.42-8.62)=900
(6)全部展开得原式=9x2+6x+1=(3x+1)平方,当x=1时等於16.
(7)1+2xy-x2-y2=1-(x2-2xy+y2)=1-(x-y)2=(1+x-y)*(1-x+y)