S
satthutamhon
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
cho a>b, b>c chứng minh rằng : ( 2a+2b+2c )^2=2abc
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