问题
解答题
计算: (1)
(2)
(3)
(4)
(5)
(6)(
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答案
(1)原式=7a-4a 3(a-4)
=
;a a-4
(2)原式=
-x2 x-1 (x+1)(x-1) x-1
=x2-x2+1 x-1
=
;1 x-1
(3)
-12 m2-9
+2m+6 m2-9 m-3 m2-9
=3-m m2-9
=-
;1 m+3
(4)原式=x2-y2 y-x
=(x-y)(x+y) y-x
=-x-y;
(5)原式=
+a2 a+1 1-a2 a+1
=
;1 a+1
(6)原式=[
-x+2 x(x-2)
]•x-1 (x-2)2 x 4-x
=[
-x2-4 x(x-2)2
]•x2-x x(x-2)2 x 4-x
=-
.1 x2-4x+4