设3a=5b=15,则1a+1b=______.-数学

题目简介

设3a=5b=15,则1a+1b=______.-数学

题目详情

3a=5b=
15
,则
1
a
+
1
b
=______.
题型:填空题难度:中档来源:不详

答案

3a=5b=
15

a=log3
15
=
lg
15
lg3
b=log5
15
=
lg
15
lg5

class="stub"1
a
+class="stub"1
b
=class="stub"lg3
lg
15
+class="stub"lg5
lg
15
=class="stub"lg15
lg
15
=class="stub"lg15
class="stub"1
2
lg15
=2.
故答案为2.

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