问题 解答题
计算下列各式值
(1)(2x)
1
4
(-3x
1
4
y-
1
3
)÷[(-27)
2
3
x-
1
2
y-
2
3
]
(2)log2
7
48
+log212-
1
2
log242
答案

(1)(2x)

1
4
(-3x
1
4
y-
1
3
)÷[(-27)
2
3
x-
1
2
y-
2
3
]

=-(2

1
4
×31-3×
2
3
)•x
1
4
+
1
4
+
1
2
 •y-
1
3
+
2
3

=-

42
3
x
3y

(2)log2

7
48
+log212-
1
2
log242=
1
2
log72
-
1
2
log(24×3)2
+
log(22×3)2
 -
1
2
log(2×3×7)2

=

1
2
log72
-
1
2
log242
-
1
2
log32
+
log222
+
log32
 -
1
2
log22
-
1
2
log32
-
1
2
log72

=-

1
2
×4+2-
1
2

=-

1
2

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