升中一數學難題

1. -6+(-3)-(-8)= -6 - 3 + 8 = -1

2. (-2)(-3)-(+2)(-4)= 6 + 8 = 14

3. (+2)-(-3)-(+4)+(-5)= 2 + 3 - 4 - 5 = -4

4. 83/3 = X+2
X = 27，所以X為27人

5. 1/5=(2x-1)/21
21 = 5(2x - 1)
21 = 10x - 5
16 = 10x
x = 1.6 or 8/5

6. 0.4y-1/2=18
0.8y - 1 = 36
0.8y = 37
y = 46.25

7. 8/z=16
8=16z
z = 0.5 or 1/2

8. 1/3(4x-3)=1
4x - 3 = 3
4x = 6
x = 3/2

9. 3.6+72%y=10.8
3.6 + 0.72y = 10.8
0.72y = 7.2
y = 7.2 / 0.72
y = 10

10. 6/z-4.4=0.4
6/z = 4.8
6 = 4.8z
z = 1.25

11. 7x-2y = 7(2) - 2(3) = 14 - 6 = 8

12. x/4+y/6= 2/4 + 3/6 = 1/2 + 1/2 = 1

13. (5x-2y)/4= ( 5(2) - 2(3) )/4 = (10 - 6)/4 = 4/4 = 1

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若果m=9,n=2和L=7

14. 3x=n+L
3x = 2 + 7
3x = 9
x = 3

15. m-x=L
9 - x = 7
x = 9 + 7
x = 16

16. 4x-3=m
4x - 3 = 9
4x = 9 + 3
4x = 12
x = 3

17. (-2)-(-4)+(-3)-5 = -2 + 4 +15 = 17

2013-08-04 16:22:34 補充：
第17題錯左...正確答案如下：
17. (-2)-(-4)+(-3)-5 = -2 + 4 -3 -5 = -6

1. -1

2. 14

3. -4

4. 27粒

5. 1/5=(2x-1)/21
21/5=2x-1
21/5+1=2x
21+1=(2x)5
22=10x
x=2.2

6. 0.4y-1/2=18
4y=18+1/2
y=18.5/4
y=4.625

7. 8/z=16
z=(16)8
z=128

8. 1/3(4x-3)=1
(4x-3)=3
4x=6
x=1.5

9. 3.6+72%y=10.8
3.6+0.72y=10.8
4.32y=10.8
y=2.5

10. 6/z-4.4=0.4
6/z=0.4+4.4
6/z=4.8
z=28.8

11. 7x-2y
=7(2)-2(3)
=8

12. x/4+y/6
=2/4+3/6
=0.5+0.5
=1

13. (5x-2y)/4
=(5x2)-(2x3)/4
=(10-6)/4
=1

14. 3x=n+L
3x=2+7
x=3

15. m-x=L
9-x=7
-x=7-9
-x=-2
x=2

16. 4x-3=m
4x-3=9
4x=12
x=3

17. -6