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

Toán Lớp 9: căn (27-12 căn 5 ) căn ( 3- căn 5)

Toán Lớp 9: căn (27-12 căn 5 )
căn ( 3- căn 5)

Comments ( 2 )

  1. $\sqrt{27-12\sqrt5}=\sqrt{ 15-2.\sqrt{15}.\sqrt{12}+12}=\sqrt{ (\sqrt{15}-\sqrt{12})^2}=\sqrt{15}-\sqrt{12}$
    $\sqrt{3-\sqrt5}=\dfrac{\sqrt{6-2\sqrt5}}{\sqrt2}=\dfrac{(\sqrt5-1)^2}{\sqrt2}=\dfrac{\sqrt5-1}{\sqrt2}=\dfrac{\sqrt{10}-\sqrt2}{2}$

  2. $\sqrt{27-12\sqrt{5}}=\sqrt{15-2.\sqrt{15}.\sqrt{12}+12}=\sqrt{(\sqrt{15}-\sqrt{12})^{2}}=\sqrt{15}-\sqrt{12}$
    $\sqrt{3-\sqrt{5}}=\sqrt{\frac{6-2\sqrt{5}}{2}}=\sqrt{\frac{5-2.\sqrt{5}.1+1}{2}}=\sqrt{\frac{(\sqrt{5}-1)^{2}}{2}}=\frac{\sqrt{5}-1}{\sqrt{2}}=\frac{\sqrt{10}-\sqrt{2}}{2}$

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