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

Toán Lớp 8: Các bạn giúp mình với y^2 – y= 3/4

Toán Lớp 8: Các bạn giúp mình với
y^2 – y= 3/4

Comments ( 2 )

  1. Giải đáp + giải thích các bước giải. Bạn học tốt.  
    y^2 – y= 3/4 $\\$ \Leftrightarrow y^2 – y – 3/4 = 0 $\\$ \Leftrightarrow y^2 – y + 1/4 – 1/4 – 3/4 = 0 $\\$ \Leftrightarrow y^2 – 2. 1/2 y – (1/2)^2 – (1/4 + 3/4) =0 $\\$ \Leftrightarrow (y-1/2)^2 – 4/4 =0 $\\$ \Leftrightarrow (y-1/2)^2 – 1 = 0 $\\$ \Leftrightarrow (y-1/2 – 1 )(y – 1/2 + 1) =0 $\\$ \Leftrightarrow ( y-3/2)(y+1/2) = 0 $\\$ \Leftrightarrow \(\left[ \begin{array}{l}y – \frac{3}{2} = 0\\y + \frac{1}{2} = 0 \end{array} \right.\) \Leftrightarrow \(\left[ \begin{array}{l}y = \frac{3}{2}\\ y = \frac{-1}{2}\end{array} \right.\) 
    $\\$ Vậy : y = 3/2 ; y = -1/2  

  2. Giải đáp:
    y^2 – y = 3/4
    <=> y^2 – y – 3/4 = 0
    <=> y^2 – 3/2 y + 1/2 y- 3/4 = 0
    <=> y ( y – 3/2 ) + 1/2 ( y – 3/2 ) =0
    <=> ( y + 1/2 )( y – 3/2 )=0
    <=> $\left[\begin{matrix} y + \dfrac{1}{2} = 0\\ y – \dfrac{3}{2} = 0\end{matrix}\right.$
    <=> $\left[\begin{matrix} y= \dfrac{-1}{2}\\ y = \dfrac{3}{2}\end{matrix}\right.$
    Vậy S={ -1/2 ; 3/2}

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

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