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

Toán Lớp 8: Tìm x biết: (3*x+1)^2 – (3*x+1)*(4*x+4) + 4*(x+1)^2 = 25*(x+3)^2.

Home/ Toán Lớp 8: Tìm x biết: (3*x+1)^2 – (3*x+1)*(4*x+4) + 4*(x+1)^2 = 25*(x+3)^2.

Toán Lớp 8: Tìm x biết: (3*x+1)^2 – (3*x+1)*(4*x+4) + 4*(x+1)^2 = 25*(x+3)^2.

Tháng Mười Một 12, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: Tìm x biết: (3*x+1)^2 – (3*x+1)*(4*x+4) + 4*(x+1)^2 = 25*(x+3)^2.

Comments ( 1 )

  1. bichhhathu
    bichhhathu
    12 Tháng Mười Một, 2022 at 10:44 chiều
    Reply
    $(3x+1)^2-(3x+1)(4x+4)+4(x+1)^2=25(x+3)^2\\↔(3x+1)^2-4(x+1)(3x+1)^2+4(x+1)^2=25(x+3)^2\\↔[(3x+1)-2(x+1)]=25(x+3)^2\\↔(3x+1-2x-2)=[5(x+3)]^2\\↔(x-1)^2=(5x+15)^2\\↔(x-1)^2-(5x+15)^2=0\\↔[(x-1)-(5x+15)][(x-1)+(5x+15)]=0\\↔(x-1-5x-15)(x-1+5x+15)=0\\↔(-4x-16)(6x+14)=0\\↔\left[\begin{array}{1}-4x-16=0\\6x+14=0\end{array}\right.\\↔\left[\begin{array}{1}4x=-16\\6x=-14\end{array}\right.\\↔\left[\begin{array}{1}x=-4\\x=-\dfrac{7}{3}\end{array}\right.$
    Vậy $x∈\left\{-4;-\dfrac{7}{3}\right\}$

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

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