sn+1=2a(n+1)+(n+1)(n+1)-3(n+1)-2an+1=sn+1-sn带入式子,化简可得an+1=2a(n+1)+2n-2-2an 2(an-2n)=a(n+1)-2(n+1)an-2n/a(n+1)-2(n+1)=1/2因此an-2n是等比数列a1-2=2an-2n=(1/2)^n-1 *2 an=(1/2)^n-1 *2+2na(n+1) -an...