InA=x InB=y In(A-B)=? 求y=Inx,x=0,y=Ina,y=Inb(b>a>0)围...

Ina-Inb=In(a-b) ?\u4e3a\u4ec0\uff1f

\u4f60\u597d\uff0c\u8bf7\u91c7\u7eb3\uff01
lna+lnb=lnab
ln(a-b)=lna/lnb(a>0,b>0,b\u22601)
\u90a3\u4e2a\u7b49\u5f0f\u4e0d\u6210\u7acb\u7684

\u7b54\uff1a
\u5982\u56fe\uff1a\u9634\u5f71\u90e8\u5206\u9762\u79ef\u4e3a\uff1a
\u222b(lna\u5230lnb)dy\u222b(0\u5230e^y)dx
=\u222b(lna\u5230lnb) e^y dy
=e^(lnb)-e^(lna)
=b-a
\u7b54\u6848\u5e94\u8be5\u662fb-a\u5427\uff1f\u9898\u76ee\u90fd\u5199b>a>0\u4e86\uff0ca-b<0\u3002

这个没有公式，只能硬算。如果是A乘或除B可以是ln AB=lnA+lnB

x/y

因为InA=x ，InB=y 所以A=e^x ,B=e^y
所以
In(A-B)=ln(e^x-e^y)

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