n is a positive integer, K the set of polynoms of real variables x1,x2,...,xn+1 and y1,y2,...,yn+1, function f:K→K satisfies
f(p+q)=f(p)+f(q), f(pq)=f(p)q+pf(q), (\forall)p,q\in K.
If f(x_i)=(n-1)x_i+y_i, f(y_i)=2ny_i for all i=1,2,...,n+1 and
i=1∏n+1(txi+yi)=i=0∑n+1pitn+1−i
for any real t, prove, that for all k=1,...,n+1f(pk−1)=kpk+(n+1)(n+k−2)pk−1