My professor yields this equation. d^2z/d0^2+1=0. This problem has to do with heat conduction. So a plane sheet -b<=x<=+b with a constant heat source Q. The equation that needs to be solved is k(d2T/dx2+Q=0. To change this equation to dimentionless, therefore lets say 0=x/b and z=(T-T(0))/(Qb^2/K). This gives d2z/d0^2+1=0. I dont not understand where the 1 comes from can someone explain?