⑩天掌 Teaching Plan on Advanced Mathematics o 两端除以y”,得y +P(x)y=e(x), d x 令z=y,则=(-D) 代入上式+(1-nP(x)z=(1-)2(x 求出通解后,将z=y代入即得 y"=3 (I-n)P(x)dx (Q(x)(1-n)e (1-n)P(x)de dx+C) tianjin polytechnic dmivendityTianjin Polytechnic University Teaching Plan on Advanced Mathematics , 1 n z y − 令 = 则 ， dx dy n y dx dz −n = (1− ) ( ) ( ), 1 P x y Q x dx dy y n n + = − − (1 n)P(x)z (1 n)Q(x), dx dz + − = − 求出通解后，将 代入即得 n z y − = 1 两端除以y n，得 代入上式 ( ( )(1 ) ). (1 ) ( ) (1 ) ( ) 1  +  −  =  = − − − − e Q x n e dx C y z n P x d x n P x d x n