2、4x-o=40),4x=L=4(0) u(x,t)=V(x,t)+W(x,t) 3、4k-0=4),4=L=42(0 2、.x-0=4(),uk=L=4,()) →Wxo=4(),W|x-L=() W(x,t)=A(t)x+B(t) →W(x,t)=4()x+2(t)-42(t)L u(x,t)=V(x,t)+W(x,t) Wxo=4(),Wx-L=4() 3、4x=0=4(t),4x=L=4,(t)) W(x,t)=A(t)x2+B(t)x W(x,0=40)x+9-4@x2 2L2 ( ), ( ) 、u u t u u t x x x L 0 1 2 u(x,t) V(x,t) W(x,t) 3 ( ), ( ) 、u u t u u t x x x x L 0 1 2 0 1 2 ( ), ( ) W u t W u t x x x L W x t A t x B t ( , ) ( ) ( ) 2 ( ), ( ) 、u u t u u t x x x L 0 1 2 1 2 2 W x t u t x u t u t L ( , ) ( ) ( ) ( ) 3 ( ), ( ) 、u u t u u t x x x x L 0 1 2 u(x,t) V(x,t) W(x,t) 0 1 2 ( ), ( ) W u t W u t x x x x L 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