log7 (56) =log7 (7*8) =log7 (7)+log7 (8) =1+log7 (8) =1+3*log7 (2) =1+3ln(2)/ln(7)而由已知得到 a=log56 (14) =ln(14)/ln(56) =[ln(2)+ln(7)]/[ln(7)+3*ln(2)];解得 aln(7)+3aln(2)=ln(7)+ln(2); ln(2)=ln(7)*(...