MathDB
Putnam 2003 A4

Source:

June 23, 2011
Putnamquadraticsfunctioncalculusderivativeinequalitiesabsolute value

Problem Statement

Suppose that a,b,c,A,B,Ca, b, c, A, B, C are real numbers, a0a \not= 0 and A0A \not= 0, such that ax2+bx+cAx2+Bx+C|ax^2+ bx + c| \le |Ax^2+ Bx + C| for all real numbers xx. Show that b24acB24AC|b^2- 4ac| \le |B^2- 4AC|