zcb602209179
幼苗
共回答了23个问题采纳率:87% 举报
(1)
a 2 -1
ab-b =
(a+1)(a-1)
b(a-1) =
a+1
b ;
a 2 -1
b+ab =
(a+1)(a-1)
b(1+a) =
a-1
b ;
ab-b
a 2 -1 =
b(a-1)
(a+1)(a-1) =
b
a+1 ;
ab-b
b+ab =
b(a-1)
(a+1)b =
a-1
a+1 ;
b+ab
a 2 -1 =
b(a+1)
(a+1)(a-1) =
b
a-1 ;
b+ab
ab-b =
b(a+1)
b(a-1) =
a+1
a-1 .
(2)原式=
a 2 -4+4
(a-2 ) 2 ÷
a
a-2
=
a 2
(a-2) 2 ×
a-2
a
=
a
a-2 .
当a=
1
2 时,原式=
1
2
1
2 -2 = -
1
3 .
1年前
7