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phineasdroid
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1. Cho a+b+c+d=0 . C/m $a^3+b^3+c^3+d^3 = 3(ac-bd)(b+d)$
2. Cho a+b+c+d=2m . C/m $(m-a)^2+(m-b)^2+(m-c)^2+(m-d)^2 =a^2+b^2+c^2+d^2$
@ chú ý: phải đánh latex
2. Cho a+b+c+d=2m . C/m $(m-a)^2+(m-b)^2+(m-c)^2+(m-d)^2 =a^2+b^2+c^2+d^2$
@ chú ý: phải đánh latex
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