Show that a ≡ -2 mod 4 implies a ≡ 0 mod 2

Question

I know that a ≡ 0 mod 2 means that a = 2n for some n

similarly a ≡ -2 mod 4 means a = -2 + 4m for some m

so n = 2m - 1 ... I am not sure how to use this to show that a ≡ -2 mod 4 implies a ≡ 0 mod 2

Any suggestions?

Answer 1

You already have $a=-2+4m$. Simply factor out a $2$.