y''-ay'^2=0y'=py''=dy'/dx=dy'/dy*dy/dx=pdp/dypdp/dy-ap^2=0dp^2/p^2=2adylnp^2=2ay+lnCp^2=Ce^(2ay)p=√Ce^(ay)dy/dx=√Ce^ay通解 -e^(-ay)=a√Cx+C1 e^(-ay)=-a√Cx-C1