因为2an-1 - 2an +3n=0
所以an=an-1 +2/3n
an - an-1 =2n/3
利用累加法
a2-a1=3
a3-a2=9/2
a4-a3=6
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an - an-1 =2n/3
累加得an-a1=[ (6+3n)(n-1)]/4=(3n^2+3n-6)/4
an=(3n^2+3n-6)/4 + 2=(3n^2+3n+2)/4
因为2an-1 - 2an +3n=0
所以an=an-1 +2/3n
an - an-1 =2n/3
利用累加法
a2-a1=3
a3-a2=9/2
a4-a3=6
.
.
.
an - an-1 =2n/3
累加得an-a1=[ (6+3n)(n-1)]/4=(3n^2+3n-6)/4
an=(3n^2+3n-6)/4 + 2=(3n^2+3n+2)/4