作业帮（x-2)^2+(x-y+1)^2+(3x-y-5)^2的最小值
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（x-2)^2+(x-y+1)^2+(3x-y-5)^2的最小值
（x-2)^2+(x-y+1)^2+(3x-y-5)^2的最小值
（x-2)^2+(x-y+1)^2+(3x-y-5)^2的最小值
利用a²+b²≥（a+b)²/2
(x-2)^2+(x-y+1)^2+(3x-y-5)^2
=（x-2)^2+(x-y+1)^2+(y-3x+5)^2
≥（x-2)^2+（(x-y+1)+(y-3x+5)）²/2…………（ x-y+1=y-3x+5时取得等号）
=（x-2)^2+(-2x+6)²/2
=3x²-16x+22
=3(x-8/3)²+2/3
≥2/3 ……（x=8/3时取得等号）
将x=8/3代入x-y+1=y-3x+5得 y=10/3.
答案是1吗？
x=3,y=4.
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