algebra help!!

Link them up together of wich one is wich.

wich one is an equasion?

wich one is an expression?

wich one is an identity?

wich one is a formula?

3x'2-2x+1

(a-b)'2=a'2-2ab+b'2

3x2-2x+1=4x-2

v=u+1
_ at'2
2​