1~ 10 ACACB DBDBC
1 1.； 12. 100; 13. 14.①③.
15. Original formula =.
16. let the quality of this rough mountain product be xkg, which means x+(3x+2000)= 10000 according to the meaning of the question.
The solution is x=2000.
Answer: The rough-machined mountain products has a mass of 2,000 kg.
17. The following figure
18.⑴A 1(0， 1) A3( 1，0) A 12(6，0)
⑵An(2n，0)
(3) upward
19. short answer: ∵OA,
OB=OC= 1500，
∴AB= (male).
A: The AB tunnel is about 635 meters long.
20. (1) Group A: median 7; Group B: average 7, median 7.
(2) (The answer is not unique)
① Because the average scores of students in Group B are higher than those in Group A, the scores of students in Group B are better than those in Group A;
② Because the average scores of students in group A and group B are not much different, and the variance of students in group B is lower than that of students in group A, it shows that the fluctuation of students' scores in group B is smaller than that in group A, so students in group B are better than those in group A;
③ Because the lowest score of students in Group B is higher than that of students in Group A, students in Group B are better than students in Group A. ..
2 1.( 1) From the meaning of the question, we can get the solution VIII.
And point A is on the function, so the solution is like this.
solve an equation
So the coordinate of point B is (1, 2).
(2) when 0 < x < 1 or x > 2, y1< y2;
When 1 < x < 2, y1> y2;
When x= 1 or x=2, y 1=y2.
22.( 1) is easy to find, so it is proved.
(2) If it is easy to prove ∽ and the similarity ratio is equal, it can be proved.
(3) 120 ,
23.( 1) If point A is AF⊥l3, point E and point F respectively, if point C is CH ⊥ l2, point H and point G respectively, it is enough to prove △ Abe △ CDG.
(2) It is easy to prove that △ Abbe △ BCH △ CDG △ DAF, two right-angled sides are h 1 and h 1+h2, and the quadrilateral EFGH is a square with a side length of h2.
So ...
3 by the meaning of the question, so.
0 < h 1
0 < h 1
When h 1=, s takes the minimum value; The first network of new curriculum standards
When < h 1
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