Mathematics Reference Answers and Grading Opinions of Grade 8 (Grade 2)
First, multiple-choice questions (this topic is entitled ***8 small questions, with 3 points for each small question and 24 points for * * *).
1.B 2。 B 3。 D 4。 C 5。 A six. A seven. B 8。 D
Fill in the blanks (this topic is entitled ***8 small questions, with 3 points for each small question and 24 points for * * *).
9.x≠ 1 10.7℃ 1 1。 If ab=0, then A = 0 12 500m 13.55.
14. 15.30 or 150 16. ① ③ ④
Third, solve the problem (this big question is ***3 small questions, 6 points for each small question, *** 18 points)
17. Solution: Original formula = …………………………………………………………………………………………….
=........................4 points.
=...................6 points.
18. solution: multiply both sides of the equation by X-2, .................. 1 min.
Get 3 = 2 (x-2)-x .................... 3 points.
The solution is x = 7, .................... 5 points.
Test: when x=7, x-2 = 5 ≠ 0. ∴ x = 7 is the solution of the original equation ............................................................................................................................
19. Solution: (1)∵, ................ 1 fraction.
Any score divided by the previous one is equal to 2 points.
(2) The seventh score is ... the seventh score.
The nth score is 6.
4. Inquiry questions (this big question is ***2 small questions, with 8 points for each small question, *** 16 points)
20. certificate: (1) in rectangular ABCD, OB=OD, AB‖CD, .................. 1.
∴∠OBE=∠ODF，∠e =∠f .∴△BOE?△DOF ...........................................................................................................
(2) When EF⊥AC, the quadrilateral AECF is a diamond, because
According to (1), △ BOE △ DOF, ∴ OE = of .........................., 5 points.
Oa = oc, ∴ quadrilateral AECF is a parallelogram, and ........................ scored 6 points.
∵EF⊥AC, ∴ quadrilateral AECF is a diamond ........................................................... 8 points.
2 1. Solution: (1) A democratic appraisal score is 25%× 100× 1=25, ...
The democratic appraisal score of B is 40%× 100× 1=40, and ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….
The evaluation score of Party C's democracy is 35%× 100× 1=35, and …………………………………………………………………………………………………………………………………………………………………………………………………………….
(2) The comprehensive score of A is MA = 25a+165 (1-a) =165-140a. ....................................................................................................
The comprehensive score of B is MB = 40a+160 (1-a) =160-120a. ......................................... has 5 points.
The comprehensive score of C is MC = 35a+170 (1-a) =170-135a. ..........................................................................................................
∵ B was finally hired, and ∴ B should have the highest comprehensive score.
From M B to MA = (160-120a)-(165-140a) = 20a-5 > 0. Get a >.
From M B to MC = (160-120a)-(170-135a) =15a-10 > 0. Get a >.
∴ If Party B is finally hired, the value range of A is < A < 1 ...........................................................................................................................................
V. Comprehensive questions (this big question * * 1 small question, ***8 points)
22. Solution: (1) From the inverse proportional function image, we get 2 =-k and ....................... 1 min.
∴ The analytical formula of inverse proportional function is .................................................................................................................................................................
From the image of linear function y = ax+b, the solution is ….
The analytical formula of ∴ linear function is y =-x+ 1 ...............................................................................................................................................
(2) The images of two functions are as shown in the figure, while B(2,-1) ......................................................................................................................................
(3) s △ AOB = s △ AOC+s △ BOC = ........................... 8 points.
Six, the topic of learning (the big topic * * 1 small topic, *** 10 points)
23.( 1) A: when point p is on the DC extension line, DF-BE = ef. ....................................................................................................................................
Certificate: In the square ABCD, there are AB=AD and ∠ Bad = 90.
That is, ∠ BAE+∠ DAF = 90 ......................, 3 points.
∵BE⊥AP,DF⊥AP,∴∠BEA=∠DFA=90。
∴∠Abe+∞∠BAE = 90。 ∴∠ Abbe = ∠ DAF .................................................................... 4 points.
∴△ Abe△ DAF .......................... 5 points.
∴BE=AF，AE = DF。 ∴ DF-BE = AE-AF = EF ..................................................................................................................................
(2) Answer: When point P is on the extension line of CD, line segments BE, DF and EF do not exist in the relationship in (1), but satisfy the relationship BE+DF = EF. ............................................................................................................