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Indian Team Selection Test 2010 ST1 P2

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May 22, 2010
algebrapolynomialquadraticsalgebra unsolved

Problem Statement

Two polynomials P(x)=x4+ax3+bx2+cx+dP(x)=x^4+ax^3+bx^2+cx+d and Q(x)=x2+px+qQ(x)=x^2+px+q have real coefficients, and II is an interval on the real line of length greater than 22. Suppose P(x)P(x) and Q(x)Q(x) take negative values on II, and they take non-negative values outside II. Prove that there exists a real number x0x_0 such that P(x0)<Q(x0)P(x_0)<Q(x_0).