来自郭良康的问题
有关均值不等式的:已知正数x.y满足xy=x+y+31求xy的范围.2求x+y的范围已知正数x.y满足xy=x+y+31求xy的范围.2求x+y的范围
有关均值不等式的:已知正数x.y满足xy=x+y+31求xy的范围.2求x+y的范围
已知正数x.y满足xy=x+y+3
1求xy的范围.2求x+y的范围
1回答
2020-05-05 22:43
有关均值不等式的:已知正数x.y满足xy=x+y+31求xy的范围.2求x+y的范围已知正数x.y满足xy=x+y+31求xy的范围.2求x+y的范围
有关均值不等式的:已知正数x.y满足xy=x+y+31求xy的范围.2求x+y的范围
已知正数x.y满足xy=x+y+3
1求xy的范围.2求x+y的范围
xy=x+y+3即x+y=xy-3≥2√(xy)令√(xy)=t则有t^2-2t-3≥0(t+1)(t-3)≥0即t≥3(舍去t≤-1)即xy=t^2≥92.xy≥9,则x+y=xy-3≥6