log3(2),log3(2^x-1),log3(2^x+11)成等差数列,则x的值为
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log3(2),log3(2^x-1),log3(2^x+11)成等差数列,则x的值为log3(2),log3(2^x-1),log3(2^x+11)成等差数列,则x的值为log3(2),log3(2
log3(2),log3(2^x-1),log3(2^x+11)成等差数列,则x的值为
log3(2),log3(2^x-1),log3(2^x+11)成等差数列,则x的值为
log3(2),log3(2^x-1),log3(2^x+11)成等差数列,则x的值为
等差
2log3(2^x-1)=log3(2)+log3(2^x+11)
log3(2^x-1)²=log3[2(2^x+11)]
所以(2^x-1)²=2(2^x+11)
令a=2^x>0
则a²-2a+1=2a+22
a²-4a-21=(a-7)(a+3)=0
a>0
a=7
所以x=log2(7)
(2^x-1)^2=2(2^x+11)
(2^x)^2-4*2^x-21=0
(2^x+3)(2^x-7)=0
2^x=-3(舍去)或2^x=7
x=log2(7)
2,2^x-1,2^x+11成等比数列
设2^x=y
2,y-1,y+11成等比数列
2(y+11)=(y-1)^2
y^2-4y-21=0
y=7
x=log2(7)
∵log3(2),log3(2^x-1),log3(2^x+11)成等差数列
∴2log3(2^x-1)=log3(2)+log3(2^x+11)
即log3[(2^x-1)^2]=log3[2*(2^x+11)]
∴(2^x-1)^2=2*(2^x+11)
令y=2^x
则
(y-1)^2=2y+22
y^2-4y-21=0
(y-7)(y+3)=0
y=7
或y=-3
∴2^x=7
或2^x=-3 (无解,舍去)
∴x=log2(7)
log3(2)+log3(x)=1,则X=?
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log3(2)+log3(x)=1,则x=?
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