设3^a=4^b=36,求2/a+1/b的值

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设3^a=4^b=36,求2/a+1/b的值设3^a=4^b=36,求2/a+1/b的值设3^a=4^b=36,求2/a+1/b的值由题可得:a=log[3]36=2log[a]6b=log[4]36

设3^a=4^b=36,求2/a+1/b的值
设3^a=4^b=36,求2/a+1/b的值

设3^a=4^b=36,求2/a+1/b的值
由题可得:a=log[3]36=2log[a]6
b=log[4]36=2log[4]6
∴所求式=2/2log[3]6+1/2log[4]6
=1/log[3]6+1/2log[4]6
=log[6]3+1/2·log[6]4
=log[6]3+log[6]2
=log[6]6
=1

3^a=4^b=36
3^a=36 两边取常用对数
lg3^a=lg36
alg3=lg36
1/a=lg3/lg36
2/a=2lg3/lg36=lg9/lg36
4^b=36两边取常用对数
lg4^b=lg36
1/b=lg4/lg36
2/a+1/b
=lg9/lg36+lg4/lg36
=(lg9+lg4)/lg36
=lg36/lg36
=1