Four Reals (Posted on 2013-05-10)

	Submitted by Bractals
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For every real x, 0 ≤ (x - ½)2 = x2 - x + ¼ or x - x2 ≤ ¼ Therefore, a - a2 ≤ ¼ b - b2 ≤ ¼ c - c2 ≤ ¼ d - d2 ≤ ¼ Adding these gives (a + b + c + d) - (a2 + b +2 c2 + d2) ≤ 1. QED

	Subject	Author	Date
	Easy way	Jer	2013-05-10 12:05:59