"You can extract it many times in the same time period", so you should put it back after each extraction.

Otherwise, it will only satisfy "equal opportunity to be extracted at any time" but not "many times to be extracted at the same time", which is the difficulty of this problem.

■ There are many ways to do this. For example, find a book with at least 1-288 pages (preferably only 1-288 pages), where 1-2 is the number 65,438+0, 3-4 is the number 2, and so on, and turn it over 30 times. The thickness of a book will be influenced by human factors.

■※ The above two methods are complicated, but because "they can be extracted many times at the same time", they are also a good method for junior high school. In addition, you can prepare 0-9 cards, draw 100 for the first time (which can be zero), draw 10 after putting it back, draw 1 0 after putting it back, and draw 31-kloc-0/44.

■ Computers are not desirable. First, some computer programs don't fetch data repeatedly, while others can; Secondly, solving problems is a process of thinking rather than actual operation, which means that there is a word "simulation experiment" in the title. In fact, you can come up with many methods, but some methods are limited to junior high school knowledge, and you can't explain them or be sure of their correctness.

2.( 1) discriminant,

△=[-(K+ 1][-(K+ 1)]-K * K-4 > = 0

2K-3≥0

K≥3/2

(2) Using the relationship between roots and coefficients

X 1+X2=K+ 1

X 1*X2= 1/4K^2

x 1^2+x2^2=(x 1+x2)^2-2*x 1*x2=(k+ 1)^2-2/4k^2 = 5

3.( 1) The percentage reduction in each period is X:

400( 1-X)( 1-X)=256

X=20%

(2) The discharge after the first stage treatment is 400( 1-20%)=320.

The total investment price is 3(400-320)+4.5(320-256)=528 (ten thousand yuan).