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 >-10000+800/(1+r)+2500/(1+r)^2 >0 .
    Question type: Inequality
    Solution:
    The inequality can be reduced to 2 inequalities：
        -2000 + 500 / ( 1 + r ) + 700 / ( 1 + r ) ^ 2 > -10000 + 800 / ( 1 + r ) + 2500 / ( 1 + r ) ^ 2         (1)
        From the definition field of divisor
         1 + x ≠ 0        (2 )
        From the definition field of divisor
         1 + x ≠ 0        (3 )
         -10000 + 800 / ( 1 + r ) + 2500 / ( 1 + r ) ^ 2 >0         (4)
        From the definition field of divisor
         1 + x ≠ 0        (5 )
        From the definition field of divisor
         1 + x ≠ 0        (6 )

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    From inequality(1)：
         r < -1.455962 或  r ＞ -0.506538
    From inequality(2)：
         r < -1 或  r ＞ -1
    From inequality(3)：
         r < -1 或  r ＞ -1
    From inequality(4)：
         -1.461597 < r < -0.458403
    From inequality(5)：
         r < -1 或  r ＞ -1
    From inequality(6)：
         r < -1 或  r ＞ -1

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    From inequalities (1) and (2)
         r < -1.455962 或  r ＞ -0.506538    (7)
    From inequalities (3) and (7)
         r < -1.455962 或  r ＞ -0.506538    (8)
    From inequalities (4) and (8)
         -1.461597 < r < -1.455962 或  -0.506538 < r < -0.458403     (9)
    From inequalities (5) and (9)
         -1.461597 < r < -1.455962 或  -0.506538 < r < -0.458403     (10)
    From inequalities (6) and (10)
         -1.461597 < r < -1.455962 或  -0.506538 < r < -0.458403     (11)

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    The final solution set is :
         -1.461597 < r < -1.455962 或  -0.506538 < r < -0.458403

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