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

Toán Lớp 7: x + -31/12 mũ 2= 49/12 mũ 2 – x= y mũ 2

Toán Lớp 7: x + -31/12 mũ 2= 49/12 mũ 2 – x= y mũ 2

Comments ( 2 )

  1. text{Giải đáp:}
    \(\Leftrightarrow y=\pm\dfrac{41}{12}\)
    text{Lời giải và giải thích chi tiết:}
    x+\(\left(\dfrac{-31}{12}\right)^2\)=\(\left(\dfrac{49}{12}\right)^2\)-x=y\(^{^{ }2}\)  
    \(\Leftrightarrow x+\left(-\dfrac{31}{12}\right)^2=\left(\dfrac{49}{12}\right)^2-x\)    
    \(\Leftrightarrow x+\left(-\dfrac{31}{12}\right)^2-\left(\dfrac{49}{12}\right)^2+x=0\)    
    \(\Leftrightarrow2x+\left(-\dfrac{31}{12}\right)^2-\left(\dfrac{49}{12}\right)^2=0\)    
    \(\Leftrightarrow2x+\dfrac{\left(-31\right)^2}{12^2}-\dfrac{49^2}{12^2}=0\)    
    \(\Leftrightarrow2x+\dfrac{\left(-31\right)^2-49^2}{144}=0\)
    \(\Leftrightarrow2x+\dfrac{961-2401}{144}=0\)
    \(\Leftrightarrow2x+\dfrac{-1440}{144}=0\)
    \(\Leftrightarrow2x+\left(-10\right)=0\)
    \(\Leftrightarrow2x=10\)
    \(\Leftrightarrow x=5\)  
    Mà: \(x+\left(-\dfrac{31}{12}\right)^2=y^2\)  
    \(\Leftrightarrow5+\dfrac{961}{144}=y^2\)  
    \(\Leftrightarrow y^2=\dfrac{1681}{144}\)
    \(\Leftrightarrow y=\pm\dfrac{41}{12}\)

  2. Giải đáp:
     
    Lời giải và giải thích chi tiết:
    x + (-31)/12^2 = 49/12^2 – x = y^2
    Ta có: x + (-31)/12^2 = 49/12^2 – x
    <=> x + (-31)/144 = 49/144 – x
    <=> x – 31/144 = 49/144 – x
    <=> x – 31/144 + x = 49/144
    <=> 2x – 31/144 = 49/144
    <=> 2x = 49/144 + 31/144
    <=> 2x = 88/144 = 5/9
    <=> x = 5/18
    Mà: 49/12^2 – x = y^2
    <=> y^2 = 49/12^2 – 5/18
    <=> y^2 = 1/16
    <=> y = \sqrt{1/16}
    <=> y =±1/4
    Vậy x = 5/18; y = ±1/4

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