||'''Book'''|| Linear Algebra ||
 ||'''Author'''|| Gilbert Strang ||
 ||'''Edition'''||  ||

/* code_begins */

{{{
e=matrix([[1,0,0],[-4,1,0],[1, 4 ,1]])
print e
e.det()}}}
If det()=1 then it is said to be as singular matrix 
upper triangular cannot be non singular matrix 
by changing the diagonal elements we can prove that it is non singular
/* code_ends */

 * '''Solution by''': 
   
   * <Shravan sanghishetty>, <Student>, <vignan>
   * <karthik.p>, <Student>, <Vignan>
   * <sridhar.b>,<student>,<Vignan>