#1){3*n+1}={4,7,10,13}
[3*n+1 for n in range(1,5)]
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sum([3*n+1 for n in range(1,5)])
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#2){3*n+5}={5,8,11,14}
[3*n+5 for n in range(4)]
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sum([3*n+5 for n in range(4)])
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#3){4-n}={4,3,2,1,0,-1}
[4-n for n in range(6)]
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sum([4-n for n in range(6)])
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#4){2,6,10,...}=?
[4*n-2 for n in range(1,6)]
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#4)13th term?
[4*n-2 for n in range(1,14)]
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#4)sum of 13 terms?
(2+50)/2*13
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#p829(52) {100,98,96,...}
[-2*n+102 for n in range(1,10)]
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#p829(52) 30th step?
[-2*n+102 for n in range(1,31)]
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#p829(52) how many bricks?
(100+42)/2*30
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#p829(53) {10,14,18,...}
[4*n+6 for n in range(1,10)]
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#p829(53) how many rows if whole section has 2040 seats?
equ=(10+(4*x+6))/2*x==2040;show(equ)
equ=expand(equ);show(equ)
equ=equ-2040;show(equ)
equ=factor(equ);show(equ)
solve(equ,x)
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[4*n+6 for n in range(1,31)]
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(10+126)/2*30
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plot(2*x^2+8*x-2040,-50,50)
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