Overview: 1 questions will be solved this time.Among them
           ☆1 inequalities

[ 1/1Inequality]
    Assignment:Find the solution set of inequality -2000+500/(1+r)+700/(1+r)^2+2000/(1+r)^3 <-10000+8000/(1+r)+2500/(1+r)^2+2000/(1+r)^3 .
    Question type: Inequality
    Solution:
    The inequality can be reduced to 1 inequality：
        -2000 + 500 / ( 1 + r ) + 700 / ( 1 + r ) ^ 2 + 2000 / ( 1 + r ) ^ 3 < -10000 + 8000 / ( 1 + r ) + 2500 / ( 1 + r ) ^ 2 + 2000 / ( 1 + r ) ^ 3         (1)
        From the definition field of divisor
         1 + x ≠ 0        (2 )
        From the definition field of divisor
         1 + x ≠ 0        (3 )
        From the definition field of divisor
         1 + x ≠ 0        (4 )
        From the definition field of divisor
         1 + x ≠ 0        (5 )
        From the definition field of divisor
         1 + x ≠ 0        (6 )
        From the definition field of divisor
         1 + x ≠ 0        (7 )

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    From inequality(1)：
         -1.198128 < r < 0.135628
    From inequality(2)：
         r < -1 或  r ＞ -1
    From inequality(3)：
         r < -1 或  r ＞ -1
    From inequality(4)：
         r < -1 或  r ＞ -1
    From inequality(5)：
         r < -1 或  r ＞ -1
    From inequality(6)：
         r < -1 或  r ＞ -1
    From inequality(7)：
         r < -1 或  r ＞ -1

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    From inequalities (1) and (2)
         -1.198128 < r < -1 或  -1 < r < 0.135628     (8)
    From inequalities (3) and (8)
         -1.198128 < r < -1 或  -1 < r < 0.135628     (9)
    From inequalities (4) and (9)
         -1.198128 < r < -1 或  -1 < r < 0.135628     (10)
    From inequalities (5) and (10)
         -1.198128 < r < -1 或  -1 < r < 0.135628     (11)
    From inequalities (6) and (11)
         -1.198128 < r < -1 或  -1 < r < 0.135628     (12)
    From inequalities (7) and (12)
         -1.198128 < r < -1 或  -1 < r < 0.135628     (13)

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    The final solution set is :
         -1.198128 < r < -1 或  -1 < r < 0.135628

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