Write the name of the school subject. You are given the first letter.

1. Learn to make things in this subject. D__________________

cmr nếu \(a\equiv b\) (mod m ), \(a⋮d\), \(b⋮d\)  và (m,n) = 1 thì \(\dfrac{a}{d}\equiv\dfrac{b}{d}\) (mod m)

Chứng minh

5n + 2 chia hết cho 2n + 9