Basic Vector and Matrix Operations

I am wondering if it is possible to perform the following two basic
functions with primitive R functions.  I know I could write functions for
either, but it seems as though they are probably built-in somewhere.

1)  Fill out a vector to a desired length with missing values or zeros.  So,

x<-c(3,4,5)
f(x,5)

3,4,5,NA,NA
  

2)  Find the [row,col] location of a particular value in a matrix, eg

x<-matrix(1:9,ncol=3)

f(x,2)

2,1
  

Thanks.