Here CRC polynomial is X4+X+1
so we can transform it to a string of binary word i.e 10010
[convert a polynomial functio to a binary word by making the places 1 which are valid for x and other places 0 starting from right hand side as place 0]
look here we have x4 so after counting from rhs ...2,1,0 like this we made the 4th one 1 ..again for X(means X1) we made the second from rhs 1 and we have already 1 here so X0 means LSB is 1..
now polynomial is 10010 (5 bit)
so we have to append (5-1)=4 0's after the data word [add n-1 0's if poly is n bit]
now the modified dataword is 11010110110000
now apply simple divide and then xor...as mentioned in book