MathDB
Linear Polynomial

Source: 1986 National High School Mathematics League, Exam Two, Problem 1

February 24, 2020
algebrapolynomial

Problem Statement

For real numbers a0,a1,,an(a0a1)a_0,a_1,\cdots,a_n(a_0\neq a_1), we haveai1+ai+1=2aia_{i-1}+a_{i+1}=2a_i for i=1,2,,n1i=1,2,\cdots,n-1. Prove that P(x)=a0Cn0(1x)n+a1Cn1x(1x)n1++anCnnxnP(x)=a_0\text{C}_n^0(1-x)^n+a_1\text{C}_n^1x(1-x)^{n-1}+\cdots+a_n\text{C}_n^nx^n is a linear polynomial.