Plz help me 1.) The Zero Divisor Theorem. If {\displaystyle M\neq 0}{\displaystyle M\neq 0} has finite projective dimension and {\displaystyle r\in R}r\in R is not a zero divisor on {\displaystyle M}M, then {\displaystyle r}r is not a zero divisor on {\displaystyle R}R.

2.)Bass's Question. If {\displaystyle M\neq 0}{\displaystyle M\neq 0} has a finite injective resolution then {\displaystyle R}R is a Cohen–Macaulay ring.

I can't
figure this out!!!?