Question

高中数学，对数的运算，错在哪里了。

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Answer 1

对数计算中，只有底数或真数的指数才能提出化简，你的答题步骤错在对需计算式子的化简上，正确解题步骤如图。

Answer 2

log2(3)=log3(3)/log3(2)=1/log3(2)=a
log3(2)=1/a
3^b=7
b=log3(7)
所以,log3(2)=1/a ,b=log3(7)
log3√7(2√21)=log√9*7(√4*21)=log3(√4*21)/log3(√9*7)
=log3(4*21)/log3(9*7)
=[log3(4)+log3(21)]/[log3(9)+log3(7)]
=[2log3(2)+log3(3*7)]/[2log3(3)+log3(7)]
=[2log3(2)+log3(3)+log3(7)]/[2log3(3)+log3(7)]
=[2log3(2)+1+log3(7)]/[2+log3(7)]
=[(2/a)+1+b]/(2+b)
=(a+ab+2)/(2a+ab)