2.2.1.2一、选择题1.下列式子中正确的个数是()①loga(b2-c2)=2logab-2logac②(loga3)2=loga32③loga(bc)=(logab)(logac)④logax2=2logaxA.0B.1C.2D.3[答案]A2.如果lgx=lga+2lgb-3lgc,则x等于()A.a+2b-3cB.a+b2-c3C.D.[答案]C[解析]lgx=lga+2lgb-3lgc=lg,∴x=,故选C.3.(2010四川理,3)2log510+log50.25=()A.0B.1C.2D.4[答案]C[解析]2log510+log50.25=log5100+log50.25=log525=2.4.已...