aa ax a at a1 a as ax a5 at as 2 ax a at aa ax a at an ax an at an 2 ax a a 010、1010 ll inds 2 ax a at 2 Ox a Ot au 1 u -a ll L.-a2u=0→l.=0 对7积分:=() 再对ξ积分: n=」/(5=(5)+A(m) →l=f(x+a)+(x-a)2 0 0 tt xx u au u − =⇒ = ξη 对 积分：u f ( ) ξ = ξ 再对 积分： 1 2 1 2 () () () ( )( ) u fdf f u f x at f x at = =+ ξξ ξ η ⇒= + + − ∫ 2 2 2 2 2 2 2 2 4 ) 1 ( 41 ) 1 ( 21) 1 ( 21 ) 1 ( 21 ) 1 ( 21 a u a u t u x a u x a t x a t u u x a t t t x x x a t t t x x tt − xx = − ∂ ∂ − ∂ ∂ = ∂ ∂ − ∂ ∂ ∂ ∂ + ∂ ∂ = ∂ ∂ ∂ = ∂ ∂ − ∂ ∂ = ∂ ∂ ∂ ∂ + ∂ ∂ ∂ ∂ = ∂ ∂ ∂ ∂ + ∂ ∂ = ∂ ∂ ∂ ∂ + ∂ ∂ ∂ ∂ = ∂ ∂ η ξ η η η ξ ξ ξ ξη η ξ