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

Toán Lớp 9: Tìm x,biết $\sqrt[]{x+4}$ – $\sqrt[]{1-x}$ = $\sqrt[]{1-2x}$

Toán Lớp 9: Tìm x,biết $\sqrt[]{x+4}$ – $\sqrt[]{1-x}$ = $\sqrt[]{1-2x}$

Comments ( 2 )

  1. #huy
    \sqrt{x+4}-\sqrt{1-x}=\sqrt{1-2x}
    <=>\sqrt{x+4}=\sqrt{1-2x}+\sqrt{1-x}
    <=>{(-4<=x<=1/2),(x+4=1-x+2\sqrt{(1-x)(1-2x)}+1-2x):}
    <=>{(-4<=x<=1/2),(\sqrt{(1-x)(1-2x)}=2x+1):}
    <=>{(-4<=x<=1/2),(x>=1/2),((1-x)(1-2x)=4x^2+4x+1):}
    <=>{(-1/2<=x<=1/2),(x=0vvx=-7/2):}
    <=>x=0
     

  2. Giải đáp: $x=0$
     
    Lời giải và giải thích chi tiết:
    $\sqrt{x+4}-\sqrt{1-x}=\sqrt{1-2x}$   ĐK: $-4\le x\le \dfrac{1}{2}$
    $\Leftrightarrow \left( \sqrt{x+4}-2 \right)+\left( 1-\sqrt{1-x} \right)+\left( 1-\sqrt{1-2x} \right)=0$
    $\Leftrightarrow \dfrac{x}{\sqrt{x+4}+2}+\dfrac{x}{1+\sqrt{1-x}}+\dfrac{2x}{1+\sqrt{1-2x}}=0$
    $\Leftrightarrow x\left( \dfrac{1}{\sqrt{x+4}+2}+\dfrac{1}{1+\sqrt{1-x}}+\dfrac{2}{1+\sqrt{1-2x}} \right)=0$
    $\Leftrightarrow x=0$ (thỏa mãn) (vế sau luôn dương)

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

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