(3)、若边界条件为: xx=0 xxl=u 作代换:l(x,t)=(x,1)+W(x,t) 得W(x,t需要满足的条件为: W1|0=()w=n(O 可令:W(x,)=A(1)x2+B()x uo(t W(x2t)=v41(1)x+-2 2L0.8 1 0.6 0.4 0.2 0 x t 0 0.5 1 1.5 2 −1 −0.5 0 0.5 1 n 10 (3)、若边界条件为： 作代换： u(x,t) = V(x,t) +W(x,t) 0 1 2 ( ), ( ) u u t u u t x x x x L = = = = 得W(x,t)需要满足的条件为： 0 1 2 ( ), ( ) W u t W u t x x x x L = = = = 可令： 2 W x t A t x B t x ( , ) ( ) ( ) = +2 1 2 1 ( ) ( ) ( , ) ( ) 2 u t u t W x t u t x x L − = +