Question Number 75616 by mr W last updated on 13/Dec/19

Commented by mind is power last updated on 13/Dec/19

Commented by mr W last updated on 14/Dec/19

Commented by peter frank last updated on 14/Dec/19

Commented by mind is power last updated on 14/Dec/19

Commented by mr W last updated on 14/Dec/19

Commented by mind is power last updated on 14/Dec/19

Commented by mathmax by abdo last updated on 15/Dec/19

Answered by mr W last updated on 14/Dec/19
![attempt an other way: let C_(n+1) =A_(n+1) +kB_(n+1) with k=constant ⇒C_n =A_n +kB_n if we can get C_(n+1) =hC_n with h=constant then we can solve both A_n and B_n . C_(n+1) =A_(n+1) +kB_(n+1) C_(n+1) =(A_n −8B_n )+k(A_n +7B_n ) C_(n+1) =(1+k)A_n +(7k−8)B_n C_(n+1) =(1+k)[A_n +((7k−8)/(1+k))B_n ] ≡C_(n+1) =h[A_n +kB_n ]=hC_n i.e. ((7k−8)/(1+k))=k ⇒k^2 −6k+8=0 ⇒(k−2)(k−4)=0 ⇒k=2 or k=4 h=1+k=3 or 5 with k=2 and h=3: C_1 =A_1 +kB_1 =2+2×1=4 C_(n+1) =hC_n =h^n C_1 =4×3^n i.e. A_(n+1) +2B_(n+1) =4×3^n ...(i) with k=4 and h=5: C_1 =A_1 +kB_1 =2+4×1=6 C_(n+1) =hC_n =h^n C_1 =6×5^n i.e. A_(n+1) +4B_(n+1) =6×5^n ...(ii) (ii)−(i): 2B_(n+1) =6×5^n −4×3^n ⇒B_(n+1) =3×5^n −2×3^n (i)×2−(ii): A_(n+1) =2×4×3^n −6×5^n ⇒A_(n+1) =8×3^n −6×5^n ⇒A_n =8×3^(n−1) −6×5^(n−1) ⇒B_n =3×5^(n−1) −2×3^(n−1)](https://www.tinkutara.com/question/Q75642.png)