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

Toán Lớp 9: \(\begin{cases} 2x+2y+xy=5\\\\27(x+y)+y^3+7= 26x^3+27x^2+9x \end{cases}\)

Tháng Tám 25, 2022 Toán học 1 Comment 0 views

Toán Lớp 9: \(\begin{cases} 2x+2y+xy=5\\\\27(x+y)+y^3+7= 26x^3+27x^2+9x \end{cases}\)

Comments ( 1 )

  1. landinhngoc97
    landinhngoc97
    25 Tháng Tám, 2022 at 4:24 chiều
    Reply
    #Mon
    \text{ Ta có:} {(2x+2y+xy=5),(27(x+y)+y^3+7=26x^3+27x^2+9x):}
    <=>{((x+y)(y+2)=9),(27(x+y)+y^3+7=26x^3+27x^2+9x):}
    <=>y^3+x^3+7+3(x+y)(x+2)(y+2)=27x^3+27x^2+9x
    <=>y^3+x^3+8xy(x+y)+12(x+y)+6(x+y)^2=(3x+1)^3
    <=>(x+y+2)^3=(3x+1)^3
    =>x+y+2=3x+1
    <=>y+1=2x
    =>(x+2)(2x+1)=9
    => \(\left[ \begin{array}{l}x=1\Rightarrow y=1\\x=-3,5\Rightarrow y=-8 \end{array} \right.\) 
    Vậy (x;y) in {(1, 1);(-3, 5, -8)}
     

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

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