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(-1)*(-3)*(4+4)=24
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（-1）*（-3）*（4+4)=24

[（-1-（-3）+4]×4=24

1: 2 × (3 × 7 - 9)
2: 2 × ((3 × 7) - 9)
3: 2 × (7 × 3 - 9)
4: 2 × ((7 × 3) - 9)
5: 3 ÷ 2 ×(7 + 9)
6: (3 ÷ 2) × (7 + 9)
7: 3 ÷ (2 ÷ (7 + 9))
8: 3 ÷ 2 ×(9 + 7)
9: (3 ÷ 2) × (9 + 7)
10: 3 ÷ (2 ÷ (9 + 7))
11: (3 × (7 - 2)) + 9
12: 3 × (7 - 2) + 9
13: (3 × (7 + 9)) ÷ 2
14: 3 × (7 + 9) ÷ 2
15: 3 × ((7 + 9) ÷ 2)
16: (3 × 7 - 9) × 2
17: ((3 × 7) - 9) × 2
18: (3 × (9 + 7)) ÷ 2
19: 3 × (9 + 7) ÷ 2
20: 3 × ((9 + 7) ÷ 2)
21: (7 - 2) × 3 + 9
22: ((7 - 2) × 3) + 9
23: (7 × 3 - 9) × 2
24: ((7 × 3) - 9) × 2
25: (7 + 9) ÷ 2 × 3
26: ((7 + 9) ÷ 2) × 3
27: (7 + 9) ÷ (2 ÷ 3)
28: (7 + 9) × 3 ÷ 2
29: ((7 + 9) × 3) ÷ 2
30: (7 + 9) × (3 ÷ 2)
31: 9 - (2 - 7) × 3
32: 9 - ((2 - 7) × 3)
33: 9 - (3 × (2 - 7))
34: 9 - 3 ×(2 - 7)
35: 9 + (3 × (7 - 2))
36: 9 + 3 ×(7 - 2)
37: 9 + (7 - 2) × 3
38: 9 + ((7 - 2) × 3)
39: (9 + 7) ÷ 2 × 3
40: ((9 + 7) ÷ 2) × 3
41: (9 + 7) ÷ (2 ÷ 3)
42: (9 + 7) × 3 ÷ 2
43: ((9 + 7) × 3) ÷ 2

（-3）×（-1）×（4＋4）