       L 10 LGI 60AA 2I I R0 A B2 LG LGI I R ...

Câu 38.        L 10 lgI 60

A

A

2

I I r

0

A

B

2 lg lg   

B

B

A

L 10 lg 40

B

I

0

 

 r 10r 1

B

A

   r 2rr r 4r

M

M

A

3

2

 L L 10 lg r 20 lg 4    

M

A

M

rL 47, 96dBChọn B.