Asumira∣b and a∣c. This means that b and c are both multiples of a, so b=am and c=an for integers m and n. Then \(b+c = am+an = a...Asumira∣b and a∣c. This means that b and c are both multiples of a, so b=am and c=an for integers m and n. Then b+c=am+an=a(m+n), so b+c is a multiple of a, or equivalently, a∣b+c. Similarly, b−c=am−an=a(m−n), so b−c is a multiple of a, which is to say a∣b−c.