题目内容
(1)计算:
-
-
+
+
;
(2)先化简,再求值:[(x+2y)(x-2y)-(x+4y)2]÷4y,其中x=5,y=2.
| 3 | -27 |
| 0 |
|
| 3 | 0.125 |
1-
|
(2)先化简,再求值:[(x+2y)(x-2y)-(x+4y)2]÷4y,其中x=5,y=2.
(1)原式=-3-0-
+0.5+
=-
;
(2)原式=(x2-4y2-x2-8xy-16y2)÷4y=(-20y2-8xy)÷4y=-4y(5y+2x)÷4y=-(5y+2x)
当x=5,y=2时,原式=-(10+10)=-20.
| 1 |
| 2 |
| 1 |
| 8 |
| 23 |
| 8 |
(2)原式=(x2-4y2-x2-8xy-16y2)÷4y=(-20y2-8xy)÷4y=-4y(5y+2x)÷4y=-(5y+2x)
当x=5,y=2时,原式=-(10+10)=-20.
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