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

Toán Lớp 8: 49x^2+14x+1=0(tìm x) x^2-5x+4 (ptđt)

Toán Lớp 8: 49x^2+14x+1=0(tìm x)
x^2-5x+4 (ptđt)

Comments ( 2 )

  1. $a)49x²+14x+1=0$
    $⇒(7x+1)²=0$
    $⇒7x+1=0$
    $⇒7x=-1$
    $⇒x=\frac{-1}{7}$
     b)x²-5x+4
    $⇒x²-x-4x+4$
    $⇒(x²-x)-(4x-4)$
    $⇒x(x-1)-4(x-1)$
    $⇒(x-1)(x-4)$

  2. ***Lời giải***
    49x^2+14x+1=0
    <=>(7x)^2+2.7x+1=0
    <=>(7x+1)^2=0
    <=>7x+1=0
    <=>7x=-1
    <=>x=-1/7
    Vậy S={-1/7}
    x^2-5x+4
    =x^2-x-4x+4
    =x(x-1)-4(x-1)
    =(x-1)(x-4)

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