> de := (1/4)*U*(diff(S(y)^4, `$`(y, 2))) = C*P1*((O*exp(G*y)-R*exp(J*y))/(P1*(exp(J*L)-exp(G*L)))+P2/P1);

print(`output redirected...`); # input placeholder
/ 2 \
1 | 2 / d \ 3 / d / d \\| /
- U |12 S(y) |--- S(y)| + 4 S(y) |--- |--- S(y)||| = C P1 |
4 \ \ dy / \ dy \ dy /// \

O exp(G y) - R exp(J y) P2\
------------------------ + --|