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x + y + z<=t,, x^2 + y^2 + z^2>=t , x^3 + y^3 + z^3<=t 2011 Romania NMO VIII p1

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August 15, 2024
algebrainequalities

Problem Statement

Find all real numbers x,y,z,t[0,)x, y,z,t \in [0, \infty) so that x+y+zt,x2+y2+z2tandx3+y3+z3t.x + y + z \le t, \,\,\, x^2 + y^2 + z^2 \ge t \,\,\, and \,\,\,x^3 + y^3 + z^3 \le t.