MathDB
integral inequality with integral condition, [0,1]->R

Source: SEEMOUS 2008 P4

June 17, 2021
calculusintegrationinequalities

Problem Statement

Let nn be a positive integer and f:[0,1]Rf:[0,1]\to\mathbb R be a continuous function such that 01xkf(x)dx=1\int^1_0x^kf(x)dx=1for every k{0,1,,n1}k\in\{0,1,\ldots,n-1\}. Prove that 01f(x)2dxn2.\int^1_0f(x)^2dx\ge n^2.