y已知F(X)=3X^2-2X,数列AN的前N项和为SN,点(N,SN)均在函数y=f(x)上,求AN BN=3/AN*A(N-1)使BN前N项和TN
问题描述:
y已知F(X)=3X^2-2X,数列AN的前N项和为SN,点(N,SN)均在函数y=f(x)上,求AN BN=3/AN*A(N-1)使BN前N项和TN
<M/20求最小正整数M
答
x=n f(x)=Sn代入函数方程:Sn=3n²-2nn=1时,S1=a1=3-2=1n≥2时,Sn=3n²-2n S(n-1)=3(n-1)²-2(n-1)Sn-S(n-1)=an=3n²-2n-3(n-1)²+2(n-1)=6n-5n=1时,a1=6-5=1,同样满足数列{an}的通项公式为an=6...