已知lna+lnb=zln(a-2b),求logz(a/b)
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已知lna+lnb=zln(a-2b),求logz(a/b)
已知lna+lnb=zln(a-2b),求logz(a/b)
已知lna+lnb=zln(a-2b),求logz(a/b)
lna+lnb=zln(a-2b)
lnab=ln(a-2b)^2
ab=(a-2b)^2
ab=a^2-4ab+b^2
a^2-5ab+b^2=0
(a/b)^2-5(a/b)+1=0
用公式法求得
a/b=5±√5^2-4*1/2=5±√21/2
logz(a/b)
=log2 (5±√21/2)
=log2 (5±√21)-1