8 令 p = x+y+z, q = x^2+y^2+z^2,以<>表示下标，则u' = u' + 2xu'u'' = u'' +2xu''+ 2u'+2x[u''+2xu'']= 2u' +u''+4xu''+4x^2u''同理u'' = 2u' +u''+4yu''+4y^2u'' u'' = 2u' +u''+4zu''+4z^2u''△u = 6u' + 3u'' + 4(x+y+z)u'' + 4(x^2+y^2+z^2)u''
+ 2xu'u'' = u'' +2xu''+ 2u'+2x[u''+2xu'']= 2u' +u''+4xu''+4x^2u''同理u'' = 2u' +u''+4yu''+4y^2u'' u'' = 2u' +u''+4zu''+4z^2u''△u = 6u' + 3u'' + 4(x+y+z)u'' + 4(x^2+y^2+z^2)u''
u'' = u'' +2xu''+ 2u'+2x[u''+2xu'']= 2u' +u''+4xu''+4x^2u''同理u'' = 2u' +u''+4yu''+4y^2u'' u'' = 2u' +u''+4zu''+4z^2u''△u = 6u' + 3u'' + 4(x+y+z)u'' + 4(x^2+y^2+z^2)u''
+2x[u''+2xu'']= 2u' +u''+4xu''+4x^2u''同理u'' = 2u' +u''+4yu''+4y^2u'' u'' = 2u' +u''+4zu''+4z^2u''△u = 6u' + 3u'' + 4(x+y+z)u'' + 4(x^2+y^2+z^2)u''
+u''+4xu''+4x^2u''同理u'' = 2u' +u''+4yu''+4y^2u'' u'' = 2u' +u''+4zu''+4z^2u''△u = 6u' + 3u'' + 4(x+y+z)u'' + 4(x^2+y^2+z^2)u''
+u''+4yu''+4y^2u'' u'' = 2u' +u''+4zu''+4z^2u''△u = 6u' + 3u'' + 4(x+y+z)u'' + 4(x^2+y^2+z^2)u''
+u''+4zu''+4z^2u''△u = 6u' + 3u'' + 4(x+y+z)u'' + 4(x^2+y^2+z^2)u''
+ 3u'' + 4(x+y+z)u'' + 4(x^2+y^2+z^2)u''
