Tính: a) A=25^log 5 6 + 49 log 7 8 -3/3^1+ log 9 4 + 4 ^2-log 2 3+5 ^ log 125 27

a) A=25log56+49log78−331+log94+42−log23+5log12527
=52log56+72log78−33⋅3log94+424log23+5log5333=5log562+7log782−33⋅3log3222+4222log23+513⋅3⋅log53=62+82−33⋅3log32+422log232+5log53=36+64−33⋅2+4232+3=976+169+3=97979=9.

b) B=36log65+101−log2−3log936log2log224
=62log65+1010log2−3log3262log2log2214=6log652+102−312⋅2⋅log36log2log2218
=52+5−3log36log218=25+5−6log22−3=24−3=−8.
c) C=log14log34.log23
=log2−2log322⋅log23=−12log22log32⋅log23=−12log22log32⋅1log32=−12log22=−12.
d) D = log₄ 2 . log₆ 4 . log₈ 6
=log42⋅log44log46⋅log46log48=log42⋅log44log48
=log42⋅log84=log84⋅log42
=log82=log232=13log22=13.