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(1)x2+2x-15=(x-3)(_____)
(2)6xy-x2-5y2=-(x-y)(_____).
(3)________=(x+2)(x-3).
(4)å解å å¼x2+6x-7=__________.
(5)è¥å¤é¡¹å¼x2+bx+cå¯å解为(x+3)(x-4), åb=_____, c=_____.
(6)è¥x2+7x=18æç«ï¼åxå¼ä¸º_____ã
(7)è¥x2-3xy-4y2=0ï¼ä¸x+yâ 0ï¼åx=_____.
(8)(x-y)2+15(x-y)+14=(_____+1)(x-y+_____).
(9)å¤é¡¹å¼ x2+3x+2, x2-2x-8, x2+x-2çå
¬å å¼ä¸º_____ã
(10)å·²ç¥a, b为æ´æ°ï¼ä¸m2-5m-6=(m+a)(m+b), åa=_____,b=_____.
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(1)è¥x2+2x+y2-6y+10=0ï¼åä¸åç»ææ£ç¡®çæ¯ï¼
ï¼ã
Aãx=1, y=3 Bãx=-1,y=-3 Cãx=-1,y=3 Dãx=1,y=-3
(2)è¥x2-ax-15=(x+1)(x-15)ï¼åaçå¼æ¯ï¼
ï¼ã
Aã15 Bã-15 Cã14 Dã-14
(3)å¦æ3a-b=2,é£ä¹9a2-6ab+b2çäºï¼
ï¼ã
Aã2 Bã4 Cã6 Dã8
(4)è¥x+y=4, x2+y2=6ï¼åxyçå¼æ¯ï¼
ï¼ã
Aã10 Bã5 Cã8 Dã4
(5)å解å å¼(x2+2x)2+2(x2+2x)+1çæ£ç¡®ç»ææ¯ï¼
ï¼ã
Aã(x2+2x+1)2 Bã(x2-2x+1)2 Cã(x+1)4 Dã(x-1)4
(6)-(2x-y)(2x+y)æ¯ä¸ååªä¸ä¸ªå¤é¡¹å¼å解å å¼çç»æï¼
ï¼ã
Aã4x2-y2 Bã4x2+y2 Cã-4x2-y2 Dã-4x2+y2
(7)è¥x2+2(m-3)x+16æ¯å®å
¨å¹³æ¹å¼ï¼åmçå¼åºä¸ºï¼
ï¼ã
Aã-5 Bã7 Cã-1 Dã7æ-1
(8)å·²ç¥x3-12x+16æä¸ä¸ªå å¼ä¸ºx+4, æå®å解å å¼ååºå½æ¯ï¼
ï¼ã
Aã(x+4)(x-2)2 Bã(x+4)(x2+x+1)
Cã(x+4)(x+2)2 Dã(x+4)(x2-x+1)
ä¸ãå å¼å解
(1) x(x+y+z)+yz
(2) x2m+xm+
(3) a2b2-a2-b2-4ab+1
(4) a2(x-y)2-2a(x-y)3+(x-y)4
(5) x4-6x2+5
(6) x4-7x2+1
(7) 3a8-48b8
(8) x2+4y2+9z2-4xy-6xz+12yz
åã解çé¢
1.å·²ç¥a2+9b2-2a+6b+2=0ï¼æ±a,bçå¼ã
2.æ±è¯ï¼ä¸è®ºxåä»ä¹æçæ°ï¼å¤é¡¹å¼-2x4+12x3-18x2çå¼é½ä¸ä¼æ¯æ£æ°ã
3.å·²ç¥n为æ£æ´æ°ï¼è¯è¯æ(n+5)2-(n-1)2çå¼ä¸å®è¢«12æ´é¤ã
4.å·²ç¥x+y=4, xy=3ï¼æ±(1) 3x2+3y2; (2) (x-y)2.
5.设a>0, b>0, c>0ä¸aãbãcä¸ä»»æ两æ°ä¹å大äºç¬¬ä¸ä¸ªæ°ï¼æ±è¯ï¼a2-b2-c2-2bc<0.
äºãå©ç¨å å¼å解计ç®ï¼
(1)å·²ç¥é¿æ¹å½¢çå¨é¿æ¯16cm, å®ç两边é¿aãbæ¯æ´æ°ï¼æ»¡è¶³a-b-a2+2ab-b2+2=0ï¼æ±é¿æ¹å½¢é¢ç§¯ã
(2)å¦å¾1ï¼ä¸æ¡æ°´æ¸ ï¼å
¶æ¨ªæé¢ä¸ºæ¢¯å½¢ï¼æ ¹æ®å¾ä¸çé¿åº¦ï¼æ±åºæ¨ªæé¢é¢ç§¯ç代æ°å¼ï¼å¹¶è®¡ç®åºå½a=2, b=0.8æ¶çé¢ç§¯ã
(3)å¦å¾2ï¼å¨åå¾ä¸ºRçåå½¢é¢æ¿ä¸ï¼å²å»åå¾ä¸ºrçå个å°åï¼å©ç¨å å¼å解计ç®å½R=7.8cm, r=1.1cmæ¶å©ä½é¨åçé¢ç§¯ï¼Ïå3.14ï¼ç»æä¿çä¸ä½æææ°åï¼ã
çæ¡ï¼
ä¸ã(1) x+5 (2) x-5y (3) x2-x-6
(4) (x+7)(x-1) (5) -1, -12 (6) -9æ2
(7) 4y (8) x-y, 14 (9) x+2 (10) -6æ1ï¼1æ-6
äºã(1)C (2)C (3)B (4)B (5)C (6)D (7)D (8)A
ä¸ã(1) (x+y)(x+z)
(2) (xm+)2
(3) (ab-1-a-b)(ab-1+a+b)
(4) (x-y)2(a-x+y)2
(5) (x+1)(x-1)(x2-5)
(6) (x2+3x+1)(x2-3x+1)
(7) 3(a4+4b4)(a2+2b2)(a2-2b2)
(8) (x-2y-3z)2
åã1ãa=1, b=-
2ãè¯æï¼-2x4+12x3-18x2=-2x2(x2-6x+9)=-2x2(x-3)2â¤0.
3ãè¯æï¼(n+5)2-(n-1)2=(n+5+n-1)(n+5-n+1)=6(2n+4)=12(n+2).
â´ (n+5)2-(n-1)2è½è¢«12æ´é¤ã
4ã(1) 30 (2) 4
5ãæ示ï¼å°æ±è¯å·¦è¾¹åç»å解æå个æ´å¼ä¹ç§¯ï¼ç¶åå©ç¨å·²ç¥æ¡ä»¶å¯¹æ¯ä¸ªå å¼ç符å·è¿è¡è®¨è®ºã
äºã(1) ç±é¢æå¾
a+b=8, (a-b+1)(a-b-2)=0,
â´ a-b=-1æa-b=2.
âµ aä¸bæ¯æ´æ°ï¼ â´a-b=-1ä¸åé¢æã
âµ a-b=2, â´ a=5, b=3.
â´ ab=15ï¼å³é¿æ¹å½¢çé¢ç§¯ä¸º15cm2ã
(2) 3.36
(3) 176cm2
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