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( 1)- 1 (2)B

Two. Bistatic navigation

1-5 CCDAB

(6) 1; -6; 7 (7)k≤2 (8)①③ (9)3/4 ( 10)

(1 1) solution: suppose the price is reduced by x yuan.

(40-x)(20+2x)= 1200

The solution is x 1= 10 (truncation).

x2=20

In order to reduce inventory as soon as possible

A: Every shirt will be reduced in price, 20 yuan.

(12) Solution: ① The ∵ equation has two unequal real roots.

∴b？ -4ac>0 ∴(-3)？ -4(m- 1)>0

∴m< 13/4

② When the ∵ equation has two equal real roots.

b？ -4ac=0 ∴(-3)？ -4(m- 1)=0

∴m= 13/4

∴ One-variable quadratic equation is X? -3x+9/4=0

The root of the equation is x=3/2.

(13) solution: ① 10 times: P = 6/ 10 = 3/5； 0 = 3/5; 20 times: p =10/20 =1/2; 30 times: p =17/30; 40 times: P=23/40

②:P= 1/2

3 not necessarily.

(14) solution: let x? +2x=y ∴y？ -7y-8=0

∴y 1=8 y2=- 1

When y=8, x? For +2x=8, X 1=2 x2=-4.

When y=- 1 For +2x=- 1, X=- 1

( 15)① 2x？ +4x+3>0

2(x？ +2x)>-3

2(x？ +2x+ 1)>-3+2

2(x+ 1)？ >- 1

(x+ 1)？ >- 1/2

∫(x+ 1)？ ≥0

No matter x is any real number, there is always 2x? +4x+3>0

②3x？ -5x- 1>2x？ -4x 7

3x？ -2x？ -5x+4x- 1+7>0

x？ -x+6>0

x？ -x>-6

(x- 1/2)？ >-23/4

∫(x- 1/2)？ ≥0

Whether x is any real number, there is always 3x? -5x- 1>2x？ -4x 7

( 16) (6,4)

Three. Knowledge development

1-4 CCDA

6 or 12 6 1: 1

(8)①PA = 1/6 PB = 2/6 = 1/3 PC = 2/6 = 1/3 PD = 1/6

(2) It's unfair, because the probability of a chess piece moving to each point is different.

If you want to win as much as possible, you should choose point B or point C.

③PA=8/36=2/9

(9)① If the diagonals of a quadrilateral are perpendicular to each other, then the area of this quadrilateral is equal to half of the diagonal product.