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(2014•唐山三模)若a>2,b>2,且12log2(a+b)+log22a=12log21a+b+log2b2,则log2(a-2)+log2(b-2)=()A.0B.12C.1D.2

题目详情
(2014•唐山三模)若a>2,b>2,且
1
2
log2(a+b)+log2
2
a
=
1
2
log2
1
a+b
+log2
b
2
,则log2(a-2)+log2(b-2)=(  )

A.0
B.
1
2

C.1
D.2
▼优质解答
答案和解析
1
2
log2(a+b)+log2
2
a
=
1
2
log2
1
a+b
+log2
b
2

∴log2(a+b)+log2
2
ab
=0,即(a+b)×
2
ab
=1,
整理得(a-2)(b-2)=4,
∴log2(a-2)+log2(b-2)=log2(a-2)(b-2)=log24=2,
故选:D.