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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