Overview: 2 questions will be solved this time.Among them
           ☆1 inequalities
           ☆1 calculations of prime factor

[ 1/2Inequality]
    Assignment:Find the solution set of inequality sqrt(x^2-1) >sqrt(2x^2+4x) .
    Question type: Inequality
    Solution:
    The inequality can be reduced to 1 inequality：
         sqrt ( x ^ 2 - 1 ) > sqrt ( 2 * x ^ 2 + 4 * x )         (1)
        From the definition field of √
         x ^ 2 - 1 ≥ 0        (2 )
        From the definition field of √
         2 * x ^ 2 + 4 * x ≥ 0        (3 )

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    From inequality(1)：
         x ＞ -3.732051
    From inequality(2)：
         x ≤ -1 或  x ≥ 1
    From inequality(3)：
         x ≤ -2 或  x ≥ 0

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    From inequalities (1) and (2)
         -3.732051 < x ≤ -1 或  x ≥ 1    (4)
    From inequalities (3) and (4)
         -3.732051 < x ≤ -2 或  x ≥ 1    (5)

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    The final solution set is :
         -3.732051 < x ≤ -2 或  x ≥ 1
[2/2 Digtal analysis]
    Work：Break 90 into prime factors.
    Question type: Resolving prime factor
    Solution:
        90=2*3*3*5
    *Note: 90 has 4 prime factors.

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