题目内容
计算:
(1)(2
-3
)÷
(2)2
×
÷(5
)
(3)先化简,再求值:(
-
)•
,其中a=2-
.
(1)(2
48 |
27 |
6 |
(2)2
12 |
| ||
4 |
2 |
(3)先化简,再求值:(
3a |
a-1 |
a |
a+1 |
a2-1 |
a |
2 |
(1)原式=(8
-9
)÷
=-
÷
=-
;
(2)原式=4
×
×
=
;
(3)原式=
•
=3(a+1)-(a-1)
=3a+3-a+1
=2a+2,
当a=2-
时,原式=4-2
+2=6-2
.
3 |
3 |
6 |
=-
3 |
6 |
=-
| ||
2 |
(2)原式=4
3 |
| ||
4 |
| ||
10 |
=
3
| ||
10 |
(3)原式=
3a(a+1)-a(a-1) |
(a+1)(a-1) |
(a+1)(a-1) |
a |
=3(a+1)-(a-1)
=3a+3-a+1
=2a+2,
当a=2-
2 |
2 |
2 |
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