T
thien0526
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
a) P_{n+3} = 720.A_n^5.P_{n-5}
b) 72.A_x^1 - A_{x+1}^3 \geq 72
c) P_x.A_{x+4}^4 \leq 42.P_{x+2}
mih k biet ghi cac c=ki hieu cua hoan vi vs chinh hop. mn thong cam va jup jum mih
b) 72.A_x^1 - A_{x+1}^3 \geq 72
c) P_x.A_{x+4}^4 \leq 42.P_{x+2}
mih k biet ghi cac c=ki hieu cua hoan vi vs chinh hop. mn thong cam va jup jum mih