a(n+2)-3a(n+1)+2an=0a(n+2)-a(n+1)=2a(n+1)-2ana(n+2)-a(n+1)=2[a(n+1)-an][a(n+2)-a(n+1)]/[a(n+1)-an]=2,为定值a2-a1=5-2=3,数列{a(n+1)-an}是以3为首项,2为公比的等比数列a(n+1)-an=3×2^(n-1)a(n+1)=an+3×2^(n...