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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 9: $\sqrt{3+2\sqrt{2}}-\sqrt{3-2\sqrt{2}}$ Rút gọn .-.

Toán Lớp 9: $\sqrt{3+2\sqrt{2}}-\sqrt{3-2\sqrt{2}}$
Rút gọn .-.

Comments ( 2 )

  1. \sqrt{3+2\sqrt{2}}- \sqrt{3-2\sqrt{2}}

    =  \sqrt{1+2\sqrt{2} +2 – \sqrt{1-2\sqrt{2}+2

    = \sqrt{(1+\sqrt{2})^{2} – \sqrt{(1-\sqrt{2})^{2}

    = |1+\sqrt{2}| – |1-\sqrt{2}|

    = 1+\sqrt{2} -(\sqrt{2}-1)

    = 1+\sqrt{2}-\sqrt{2}+1

     = 2

  2. $\sqrt[]{3+2\sqrt[]{2}} – \sqrt[]{3-2\sqrt[]{2}}$ 
    $ = \sqrt[]{( \sqrt[]{2} )^2 + 2 . \sqrt[]{2} . 1 + 1^2} – \sqrt[]{( \sqrt[]{2} )^2 – 2 . \sqrt[]{2} . 1 + 1^2}$
    $ = \sqrt[]{( \sqrt[]{2} + 1 )^2} – \sqrt[]{( \sqrt[]{2} – 1 )^2} $
    $ = | \sqrt[]{2} + 1 | – | \sqrt[]{2} – 1 | $
    $ = \sqrt[]{2} + 1 – ( \sqrt[]{2} – 1 )$
    $ = \sqrt[]{2} + 1 – \sqrt[]{2} + 1 $
    $ = 2 $
     

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222-9+11+12:2*14+14 = ? ( )