Question

高二数学 红对勾 练习

Answer 1

(1)A(n+2)=5/3A(n+1)-2/3AnA(n+2)-A(n+1)=2/3A(n+1)-2/3An=2/3[A(n+1)-An]∴{Bn=A(n+1)-An}是等比数列，q=2/3Bn=A(n+1)-An=(A2-A1)q^(n-1)=(2/3)^n(2)A2-A1=2/3，A3-A2=(2/3)^2，A4-A3=(2/3)^3，……，An-A(n-1)=(2/3)^(n-1)连加得An-A1=2/3+(2/3)^2+(2/3)^3+……+(2/3)^(n-1)=2-2(2/3)^(n-1)An=3-2(2/3)^(n-1)Sn=3-2×1+3-2×2/3+3-2(2/3)^2+……+3-2(2/3)^(n-1) =3n-2[1+2/3+(2/3)^2+……+(2/3)^(n-1)] =3n-6+6(2/3)^n

Answer 2

必修几，多少页，哪到题