exponential function

(a+b)^-1/a^-1+b^-1
=a/(a+b)+1/b
=(ab+a+b)/(a(a+b))

if you asked "(a+b)^-1/(a^-1+b^-1)":

(a+b)^-1/(a^-1+b^-1)
=(1/(a+b) )/ (a+b)/(ab))
=ab/(a+b)^2

小紫雲　星空副帳 講得好岩, 括號必須清晰~

>> (a+b)^-1直接得出1/(a+b)?
>> 正確!