UC知道：想知道神马，提问回答学习问题百度都知道

1/x +4/y =9,x>0,y>0.求x+y的最小值

来源：百度知道编辑：UC知道时间：2024/06/14 11:34:27

1/X+4/y=9.===>9(x+y)=(x+y)(1/x+4/y)=5+[(4x/Y)+(Y/X)]>>5+4=9.===>(X+Y)min=1.

1/x +4/y =9,
4x+y = 9xy
4x+y ≥ 2√4xy = 4√xy
9xy≥4√xy
√xy≥4/9

x+y ≥ 2√xy ≥ 8/9

我没想清楚，解错了，还是看楼上的吧

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