Question

计算1. 2log以5为底10+log以5为底0.25 2. 已知lg2=0.3010，lg3=0.4771,求lg根号下45

Answer 1

1. 2log以兆亏5为底10+log以5为底0.25
=log以5为底100+log以5为底0.25
=log以5为运塌底25
=2
2. lg根号下45
=(lg45)/2
=(lg5+lg9)/2
=(1-lg2+2lg3)/族悄神2
=(1-0.3010+2×0.4771)/2
=0.9971

Answer 2

2log以5为底10+log以念掘嫌5为底仔手散老0.25 =log5(100*0.25)=2
lg45=lg9*5=2lg3*lg52=2lg3(1-lg2)= 0.6670

追问

2.是求lg根号45哇？？

追答

你将根号下45=45^1/2
lg45^1/2=1/2lg45=1/2*2lg3(1-lg2)= lg3(1-lg2)=0.6670 /2=0.3335