lim [a^(n+2)-b^(n+3)]/[a^n+b^(n+1)](a>0,b>0)

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lim[a^(n+2)-b^(n+3)]/[a^n+b^(n+1)](a>0,b>0)lim[a^(n+2)-b^(n+3)]/[a^n+b^(n+1)](a>0,b>0)lim[a^(n+2)-b^

lim [a^(n+2)-b^(n+3)]/[a^n+b^(n+1)](a>0,b>0)
lim [a^(n+2)-b^(n+3)]/[a^n+b^(n+1)](a>0,b>0)

lim [a^(n+2)-b^(n+3)]/[a^n+b^(n+1)](a>0,b>0)
此题要分三种情况求解.
(1)当0∞)[(b/a)^n]=0)
=a²
(2)当0∞)[(a/b)^n]=0)]
=-b³/b
=-b²
(3)当a=b时,
原式=lim(n->∞){[a^(n+2)-a^(n+3)]/[a^n+a^(n+1)]}
=lim(n->∞)[(a²-a³)/(1+a)]
=a²(1-a)/(1+a)