MathDB
broken computer does not allow for all operations

Source: China TST 1988, problem 8

June 27, 2005
algebrapolynomialinductionalgebra unsolved

Problem Statement

There is a broken computer such that only three primitive data cc, 11 and 1-1 are reserved. Only allowed operation may take uu and vv and output uv+v.u \cdot v + v. At the beginning, u,v{c,1,1}.u,v \in \{c, 1, -1\}. After then, it can also take the value of the previous step (only one step back) besides {c,1,1}\{c, 1, -1\}. Prove that for any polynomial Pn(x)=a0xn+a1xn1++anP_{n}(x) = a_0 \cdot x^n + a_1 \cdot x^{n-1} + \ldots + a_n with integer coefficients, the value of Pn(c)P_n(c) can be computed using this computer after only finite operation.