(MP)L=Q的导数=20-12L(以K 为常数)、同理(MP)K=50-4K(以L为常数)
建立方程:660=15L+30K, ( 20-12L)/15=(50-4K)/30
解得,L= 3 K=41/2=20.5
这两个方程的公式你自己依上面所列的推理吧,我就不打了,希望帮到你
Lagrangian
Lgr = 20L + 50K - 6L^2 - 2K^2 + t(660 - 15L - 30K)
FONC's
dLgr/dL = 20 - 12L - 15t = 0, ie. L = (20 - 15t) / 12
dLgr/dK = 50 - 4K - 30t = 0, ie. K = (50 - 30t) / 4
into the budget constraint
660 = 15 * (20 - 15t) / 12 + 30 * (50 - 30t) / 4
t = - 208/195
plug back to FONC's
L = 3, K = 41/2