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＋800/1+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 + 800 / 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 )

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    From inequality(1)：
         r < -1.483494 或  r ＞ -0.516506
    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

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    From inequalities (1) and (2)
         r < -1.483494 或  r ＞ -0.516506    (6)
    From inequalities (3) and (6)
         r < -1.483494 或  r ＞ -0.516506    (7)
    From inequalities (4) and (7)
         r < -1.483494 或  r ＞ -0.516506    (8)
    From inequalities (5) and (8)
         r < -1.483494 或  r ＞ -0.516506    (9)

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    The final solution set is :
         r < -1.483494 或  r ＞ -0.516506

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