Which of the equations are true identities?
\begin{aligned} \text{A. }&n(n-2)(n+2)=n^3-4n \\\\ \text{B. }&(x+1)^2-2x+y^2=x^2+y^2+1 \end{aligned}
A.
B.
​

n(n−2)(n+2)=n
3
−4n
(x+1)
2
−2x+y
2
=x
2
+y
2
+1
​