êÆ©ÛSK: 1 9 ±
r\r
http://math.nju.edu.cn/˜meijq 2007.4
`²: kSK´7L3þþ,gKÐ ±·,
7L´îÕá¤.
SK:
1. x,yþmX þSÈ, x, yPX, y0. 3e¡Øª
xxty, xtyy¥0
¥-t xx, yy
xy, yy l y²Schwarzت. 2. y²SÈm÷vXe²1o>/úª:
}x y}2 }xy}22p}x}2 }y}2q, @ x, y.
3. apa1, a2,, anqPRn, r¡0,-
In txpx1, x2,, xnqPRn
|xiai|¤r, 1¤i¤nu,
¡nN.y²NÑ´48. rþª¥¤¤ 8 Ü¡máN,y²§(´m8.
4. AÝþm pX, ρqf8, 3AAþ½ÂXeNρA:
ρApa1, a2qρpa1, a2q, y²ρAAþÝþ,¡pÝþ.
5. y²Cauchy:XJkÂñf, KÙg´Âñ.
1
6. y²,k;8Ü8Ú¿8E;8Ü.
7. f : XÑY lÝþmÝþmN. y²,
p1qf ëYN¿©7^´m8´m8;
p2qf ëYN¿©7^´48´48.
8. Þ~`²,lR2 RëYNؽr48N48(J«: Ä
¼êfpxqx1 ã,¿x¶ÝK).
9. y²,Ø3lü ±S1 RëYü(J«: Äfpxqfpxq,
xÚx¿ÄÎÒCz.)
10. äe4´Ä3, X3KOÑ5:
p1q lim
px,yqÑp0,0q
sin xy
a
x2 y2, p2q lim
px,yqÑp0,0q
x2y2 x2 y2,
p3q lim
px,yqÑp0,0qx2logpx2 y2q, p4q lim
px,yqÑp0,0q
x3 y3 x2 y .
11. äe4´Ä3, X3KOÑ5:
p1qlimxÑ8limyÑ8x2 y2
x2 y4, limyÑ8limxÑ8x2 y2 x2 y4,
p2qlimxÑ 8limyÑ0 xy
1 xy, limyÑ0limxÑ 8 xy 1 xy,
p3qlimxÑ8limyÑ8sin2x yπx , limyÑ8limxÑ8sin2x yπx ,
p4qlimxÑ0limyÑ8 1
xytan1xyxy, limyÑ8limxÑ0 1
xytan1xyxy. gK:
1. y², Rn ¥m¥ØU¤eZpØ4¥¿.
2. p1qy²,3Rnpn¥2q¥Kk: e8Ü´´ëÏ.
p2q|^\®²y²¯¢y², lRnpn¥2q RëYNØU
ü.
3. fp0q0, f : RnÑRn ±ålN,=
}fpxqfpyq}}xy}, @x, yPRn, y²f 5C.
2