lineare substitution

[bhelmes]

A peaceful and pleasant night for you,

Let f(n)=2n²-1 n=a+bk
then f(a+bk)=2(a+bk)²-1= 2(a²+2abk+b²k²)=2a²+4abk+2b²k²=g(k)

if t|f(n) for which k t|g(k) ?

I am today a little bit stupid and if someone could give me a hint, it would be nice.

[bhelmes]

Solving the linear substitution to k will do it.

[bhelmes]

A friendly good night for you

Let f(n)=2n²-1 and t|f(no)
g(k)=2k²-1 - C where C is a constant
for which k0 t|g(ko) ?

this is not a linear substitution and I will be glad knowing the answer.