Overview: 5 questions will be solved this time.Among them
           ☆2 inequalities
           ☆1 equations
           ☆1 arithmetic calculations
           ☆1 convert the decimals to fractions

[ 1/5 Digital analysis ]
    Work: Convert decimal 0.2|09 to fractional form.
    Question type: Convert decimal to fraction
    Solution:

0.2|09=

23 110

    *Note: Convert circular decimal to fraction.
[2/5 Formula]
    Work: Calculate the value of equation (5-1)/2 .
    Question type: Mathematical calculation
    Solution:
          (5-1)/2
        =4/2
        =2
    Answer:(5-1)/2=2
[ 3/5 Equation]
    Work: Find the solution of equation a^2 = -1 .
    Question type: Equation
    Solution:    This equation has no real solution!
[ 4/5Inequality]
    Assignment:Find the solution set of inequality a^2 ≥-1 .
    Question type: Inequality
    Solution:
    The inequality can be reduced to 1 inequality：
         a ^ 2 ≥ -1         (1)

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    From inequality(1)：
         a ∈ R (R is all real numbers),that is, in the real number range, the inequality is always established!

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    The final solution set is :
         a ∈ R (R is all real numbers),that is, in the real number range, the inequality is always established!
[ 5/5Inequality]
    Assignment:Find the solution set of inequality 1 ≥a^3 ≥-1 .
    Question type: Inequality
    Solution:
    The inequality can be reduced to 2 inequalities：
        1 ≥ a ^ 3         (1)
         a ^ 3 ≥ -1         (2)

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    From inequality(1)：
         a ≤ 1
    From inequality(2)：
         a ≥ -1

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    From inequalities (1) and (2)
         -1 ≤ a ≤ 1    (3)

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    The final solution set is :
         -1 ≤ a ≤ 1

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