Срочно помогите пжпж

я такое в 3 классе решал

u(x, y) = X(x)Y(y)



X''''(x)Y(y) + 2X''(x)Y''(y) + X(x)Y''''(y) - 3(X''(x)Y(y) + X(x)Y''(y)) = 0



X''''(x)/X(x) + 2X''(x)Y''(y)/(X(x)Y(y)) + Y''''(y)/Y(y) - 3(X''(x)/X(x) + Y''(y)/Y(y)) = 0



X''''(x)/X(x) - 3X''(x)/X(x) = -λ
Y''''(y)/Y(y) + 2Y''(y)/Y(y) - 3Y''(y)/Y(y) = λ



X''''(x) - 3X''(x) = -λX(x)



m^4 - 3m^2 + λ = 0

Брат сам проверь лучше