Let A_0=6 A_1=5 A_n=A_(n-1)+A_(n-2) for n>=2.

Let
 A_0=6   
A_1=5   
A_n=A_(n-1)+A_(n-2) for n>=2. 
                                                                                      Λ
There is a unique ordered pair (c,d) such that c∅^n+d∅^n is the clsed form for sequence A_n.

find c using Fibonacci and Lucas number sequence.