问题
解答题
计算: (1)(2
(2)已知log73=a,log74=b,求log4948.(其值用a,b表示) |
答案
(1)原式=(
)9 4
-1-(1 2
)-27 8
+(2 3
)-2+|1-3 2
|2
=[(
)2]3 2
-1-[(1 2
)3]-3 2
+2 3
+4 9
-12
=
-1-3 2
+4 9
+4 9
-12
=
-2
.1 2
(2)
log4948=
log7(3×16)=1 2
(log73+log716)1 2 =
(log73+2log74)1 2
=
(a+2b).1 2