Question

bài 4 ạ

Answer 1

`a)` Ta có: `a:5` dư `4`

`=> a=5k+4(k` ∈ `Z)`

`=> a^2=25k^2 +20k+25k+16` chia `5` dư `1`

`b) =(x-3)^2 +1 >=0+1=1>0`

`c) =-(x+2)^2 -1<=0-1=-1<0`