问题 解答题
计算:
(1)(
48
+
1
4
6
)÷
27

(2)已知x=2+
5
,y=2-
5
,求x2-y2
的值.
答案

(1)(

48
+
1
4
6
)÷
27

=

48
27
+
1
4
6
27

=

16
9
+
1
4
2
9

=

4
3
+
1
12
2

(2)x2-y2

=(x+y)(x-y),

=(2+

5
+2-
5
)(2+
5
-2+
5
),

=8

5

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