(2)3+x+2x+1=31

3x=27

x=9

(3)2006÷4余2

∴32006的末位数为9

(4)2n=x3m×x2n

(5)①<<<<< ②nn+1<(n+1)n ③<

(6)①=n2+7n-n2-n-6∵n为自然数

=6n-6 ∴n-1也为整数

6n-6/6=n-1 ∴该式的值能被b整除

②(x+a)(x+b)

= x2+(a+b)x+ab

∴a+b=m=x

Ab=36

∴m=12

第53-55页

1选择题

(1)D(2)B ( 3)B (4)C (5)C (6)C(7)C (8) C (9) B

2.填空题

(1) x3+y3 (2) -3a-1 (3) x=2 (4)x4-1 (5)100-1 100+1 9999

(6)-9a2+b2c2 (7) 2y2 (8) -7p-q2 (9) 3 (10)4m2+4m+1 (11) x4-a4

(12) a2-b2+2bc-c2

3.解答题

(1)① 原式=a3b3ⅹa2b2ⅹa4b8c2=a9b12c2

②原式=-3x2y2+3x3y+6x3y4-3xy

③原式=a3-a+3a2-3-2a3+8a2+a-4=-a3+11a2-7

④原式=4m2-9n2

⑤原式=y4-9x4

⑥原式=(4x2-1)2=16x4-8x2+1

(2)①原式=(1000+3)(1000-3)=999991

②原式=2006/20062-(2006+1)(2006—1)=2006

(3) 原式=[x+(y+z)][x-(y+z)]=x2-(y+z)2=x2-y2-z2-2yz

(4)全对

(5)(x+y)2-(x-y)2=4xy

xy=[(2a)2-(2b)2]=a2-b2

(6) (a-1/a)2=a2+1/a2-2a 1/a

a2+1/a2=(a-1/a)2+2=16+2=18

(7) (a+b+c)2=a2+b2+c2+2ab+2ac+2bc

(2x-y+3z)2=4x2+y2+9z2-4xy+12xz-6yz