P
phuong_phuong_phuong
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
giải pt
cos6x - cos4x + 4cos3x + 4 = 0
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cos6x - cos4x + 4cos3x + 4 = 0
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