# Reduce relations with Fibonacci function never terminates,

i have a reduce operation which includes Fibonacci function. but the problem is it never terminates, i tried some modifications, for example removing f1 in my relation. sometimes it works and at least it gives me an output. but the relation itself MUST NOT change and i dont want to modify the expressions. Could you help me what the problem is, seems it is a loop or something? This expression cause the problem f1*Fibonacci[1 + j - N], also f1*Fibonacci[j - N]]].

NONE of the expressions must change, every single expression is needed and no add/remove/modification is allowed

Reduce[Exists[{i, f, j, f1, f2, N},
i == iPP && f == fPP && j == jPP && f1 == f1PP && f2 == f2PP &&
N == NPP && j >= N && iP == i + j - N && jP == N &&
f1P == f2* Fibonacci[j - N] + f1*Fibonacci[1 + j - N] &&
f2P == f2 *Fibonacci[-1 + j - N] + f1*Fibonacci[j - N]]]

• Reduce has the form: Reduce[expr, variables]. You do not specify any variables. Jan 14 at 16:06
• N has a predefined meaning in Mathematica and should not be used as a user-defined symbol. Jan 14 at 16:17

Reduce[Exists[{i, f, j, f1, f2, N},