那么(1-a)
=(1-a)(a-1)
=-(a-1)(a-1)
=-(a-1)=-.
答案:-
6.解析:原式=+ =(-1)+(+1)=2.
答案:2
7.解:∵x+x=3,
∴(x+x)2=9,
∴(x)2+2x·x+(x)=9,
即x+2+x-1=9,∴x+x-1=7,
∴原式==.
8.解:(1)原式=ab·(-3ab)·(3ab)
=(-3×3)ab
=-9a1b0
=-9a.
(2)原式=(0.43)-1+[()4]+(0.12)
=0.4-1-1++0.1
=3.1.
9.解:==.
∵a,b是方程x2-6x+4=0的两根,