Hello,

Can anyone help me with any of the foolowing proofs

For any integers a,b,c,d

Thank you

a| 0, 1 |a,a|a.a| 1 if and only ifa=+/-1.- If
a|bandc|d, thenac|bd.- If
a|bandb|c, thena|c.a|bandb|aif and only ifa=+/-b.- If
a|bandbis not zero, then |a|<|b|.- a+b is integer, a.b is integer