Optellen en aftrekken (reeks 3)

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1. \(-9-4+4+9-2=\)
2. \(8-8+4-3-8=\)
3. \(6-9+1-4-7=\)
4. \(-(+3)-(-8)+(+1)+(+9)-(+1)=\)
5. \(+(+7)-(+2)-(+6)-(-7)+(-1)=\)
6. \(-(-9)+(-5)+(+1)+(+7)+(+1)=\)
7. \(7+1+3+6+9=\)
8. \(-7+1+1+5+4=\)
9. \(+(+4)-(-2)-(+5)+(+7)-(-6)=\)
10. \(-(+1)+(+1)+(-2)-(-4)+(+8)=\)
11. \(9-9+2-3+8=\)
12. \(+(+8)+(-2)-(+1)+(+9)-(-7)=\)

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Verbetersleutel

1. \(-9-4+4+9-2=-2\)
2. \(8-8+4-3-8=-7\)
3. \(6-9+1-4-7=-13\)
4. \(-(+3)-(-8)+(+1)+(+9)-(+1)=-3+8+1+9-1=14\)
5. \(+(+7)-(+2)-(+6)-(-7)+(-1)=+7-2-6+7-1=5\)
6. \(-(-9)+(-5)+(+1)+(+7)+(+1)=+9-5+1+7+1=13\)
7. \(7+1+3+6+9=26\)
8. \(-7+1+1+5+4=4\)
9. \(+(+4)-(-2)-(+5)+(+7)-(-6)=+4+2-5+7+6=14\)
10. \(-(+1)+(+1)+(-2)-(-4)+(+8)=-1+1-2+4+8=10\)
11. \(9-9+2-3+8=7\)
12. \(+(+8)+(-2)-(+1)+(+9)-(-7)=+8-2-1+9+7=21\)