tieyaozh
幼苗
共回答了21个问题采纳率:85.7% 举报
y2-y1=f(x2)-f(x1)=log(a)(a^x2-1)-log(a)(a^x1-1)
=log(a)[(a^x2-1)/(a^x1-1)]
设x1<x2,那么;a^x2>a^x1,a^x2-1>a^x1-1
(a^x2-1)/(a^x1-1)>1
log(a)[(a^x2-1)/(a^x1-1)]>0
y2-y1>0
∴斜率=(y2-y1)/(x2-x1)>0
同理:x1>x2时,那么;a^x2<a^x1,a^x2-1<a^x1-1
(a^x2-1)/(a^x1-1)<1
log(a)[(a^x2-1)/(a^x1-1)]<0
y2-y1<0
∴斜率=(y2-y1)/(x2-x1)>0
1年前
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