计算下列各式的值. (1)lg12.5-lg
(2)2log510+log50.25; (3)2log32-log3
|
(1)lg12.5-lg
+lg5 8
=lg(12.5÷1 2
×5 8
)=lg10=1;1 2
(2)2log510+log50.25=log5102+log50.25=log5(102×0.25)=log525=log552=2log55=2×1=2;
(3)2log32-log3
+log38-332 9
=2log32-(log332-log39)+log323-3
=2log32-log325+log332+3log32-3
=2log32-5log32+2+3log32-3
=-1.