%% 2010 ~ 2011academic year seventh-grade people's education edition ● Reference answer

No. 13

The first volume of grade seven, chapter 3.3

Reference answer for proficiency test

I. 1. C 2。 C 3。 C 4 explosive B 5。 A six. B 7。 An eight. C

2.9.x = -7 10. 10, the attribute of equation 2.

1 1.-2 12.5 13.4 14.4 15.20

16.2(x- 1)+3x = 13

Third, 17. ( 1)x =- 1； (2)x = 2.7

18. From the meaning of the title, 2 m +5 +2m -( 1= 2 1. The solution is m = 2.2).

19. Suppose the length of the train is x meters. According to the meaning of the question, x+600 = X. The solution is x = 120.305.

Therefore, the train length is120m.

4.20.( 1) is incorrect; ①;

(2) (1) When the denominator is removed, the multiplication term cannot be omitted;

When the factor outside the bracket is negative, the sign of each item in the bracket will change after the bracket is removed.

(3) Divide by the denominator to get 3(x+ 1)-2(2 -3x)= 6.

Without brackets, 3x+3 -4 +6x = 6.

When the item is shifted, 3x+6x = 6 -3 +4.

Combine similar projects and you get 9x = 7.

The coefficient is 1 and x =7.9.

2 1. Suppose the water velocity is x km/h, and according to the meaning of the question, 8(20+x)= 12(20-x). The solution is x = 4.

Then 8(20+x)= 8 ×(20 +4)= 192.

Therefore, when the current speed is 4 km/h, the distance between pier A and pier B is 192 km.

22. From the meaning of the question, we get 3 (x+2)-2 [3 (x+2)-2] = 4. We get x = -2.

So the value of x in the equation is -2.

23. If the horse carries X packages and the mule carries (x+2) packages. According to the meaning of the question, it is 2(x- 1)= x+2+1. The solution is x = 5. Then x+2 = 7.

So the horse carried five bags and the mule carried seven bags.