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

Toán Lớp 8: a. (x+1)(x-4) – x2 = 0 b) (2x-1)(x-3) – 2(x+1) 2 =0 c) x2 – 25 –( x+5 ) = 0 d. 3x(x-2) – x+ 2 = 0

Tháng Sáu 4, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: a. (x+1)(x-4) – x2 =
0
b) (2x-1)(x-3) –
2(x+1) 2 =0
c) x2 – 25 –( x+5 ) = 0
d. 3x(x-2) – x+ 2 = 0

Comments ( 2 )

  1. hienthucthu97
    hienthucthu97
    4 Tháng Sáu, 2022 at 12:25 sáng
    Reply
    Bạn tham khảo nhé.
    (x+1)(x-4)-x^2=0
    <=>x^2-4x+x-4-x^2=0
    <=>-3x=4
    <=>x=-4/3
    Vậy x=-4/3
    $\\$
    (2x-1)(x-3)-2(x+1)^2=0
    <=>2x^2-6x-x+3-2(x^2+2x+1)=0
    <=>2x^2-7x+3-2x^2-4x-2=0
    <=>-11x+1=0
    <=>-11x=-1
    <=>x=1/11
    Vậy x=1/11
    $\\$
    x^2-25-(x+5)=0
    <=>(x-5)(x+5)-(x+5)=0
    <=>(x+5)(x-5-1)=0
    <=>(x-6)(x+5)=0
    <=>[(x-6=0),(x+5=0):}
    <=>[(x=6),(x=-5):}
    Vậy x\in{6;-5}
    $\\$
    3x(x-2)-x+2=0
    <=>3x(x-2)-(x-2)=0
    <=>(x-2)(3x-1)=0
    <=>[(x-2=0),(3x-1=0):}
    <=>$\left[\begin{matrix} x=2 \\ x=\dfrac{1}{3}\end{matrix}\right.$
    Vậy x\in{2;1/3}

  2. khanhlanchau
    khanhlanchau
    4 Tháng Sáu, 2022 at 12:25 sáng
    Reply
    a)(x+1)(x-4)-x^2=0
    ⇔x^2-4x+x-4-x^2=0
    ⇔-3x=4
    ⇔x=-4/3
    Vậy S={-4/3}
    b)(2x-1)(x-3)-2(x+1)^2=0
    ⇔2x^2-6x-x+3-2(x^2+2x+1)=0
    ⇔2x^2-7x+3-2x^2-4x-2=0
    ⇔-11x=-1
    ⇔x=1/11
    Vậy S={1/11}
    c)x^2-25-(x+5)=0
    ⇔(x-5)(x+5)-(x+5)=0
    ⇔(x+5)(x-5-1)=0
    ⇔(x+5)(x-6)=0
    $⇔$\(\left[ \begin{array}{l}x+5=0\\x-6=0\end{array} \right.\) 
    $⇔$\(\left[ \begin{array}{l}x=-5\\x=6\end{array} \right.\) 
    Vậy S={-5;6}
    d)3x(x-2)-x+2=0
    ⇔3x(x-2)-(x-2)=0
    ⇔(x-2)(3x-1)=0
    ⇔\(\left[ \begin{array}{l}x-2=0\\3x-1=0\end{array} \right.\) 
    ⇔\(\left[ \begin{array}{l}x=2\\x=\dfrac{1}{3}\end{array} \right.\) 
    Vậy S={2;1/3}
     

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

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