||'''Book'''|| Advanced Engineering Mathematics ||
 ||'''Author'''|| Erwin Kreyszig ||
 ||'''Edition'''|| 8th Edition ||

/* code_begins */

{{{
#unsolved
#prob:-7
x = var('x') 
k = var('k') 
y = function('y',x)
sol=desolve(diff(y,x,x) + k*y - exp(-k*x), [y,x])
sol
# This was a first order differential equation, which was solved by sage. I made it a second order differential eqn (simply by substituting the first order derivative by second order derivative). Sage prompted  us "Is k positive,negative or zero"
}}}

/* code_ends */

 * '''Solution by''': 
   * Aashita Kesarwani, Student, IIT Roorkee.
   * Praveen Kumar, Student, IIT Roorkee
   * Swati Ahuja,Student,IIT Roorkee