1.整式-(an+1)(an-1)+(an)2(n∈N)化简的结果是 ( )
A.1 B.0 C.-1 D.±1
【解析】选A.-(an+1)(an-1)+(an)2=-(a2n-1)+a2n
=-a2n+1+a2n=1.
【加练·固】
若x+y=2,xy=-2,则(1-x)(1-y)的值是 ( )
A.-1 B.1 C.5 D.-3
【解析】选D.(1-x)(1-y)
=1-x-y+xy
=1-(x+y)+xy
=1-2+(-2)=-3.
2.方程x2+2x-3=0的解集为 ( )
A.{-1,3} B.{1,-3}
C.{-1,-3} D.{1,3}
【解析】选B.因为x2+2x-3=0,
所以(x-1)(x+3)=0,
x1=1,x2=-3.