The number of terms in the expansion of the multinomial (x + y + z)n
12(n+1)(n+2)
12n(n+1)
12(n+1)(n+3)
none of these
Number of terms in (x+y+z)n
= number of non-negative integral solution of p+q+r=n
=n+2C2=12(n+2)(n+1)