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

Toán Lớp 8: Câu 1 (2 điểm) Phân tích đa thức thành nhân tử a. 8x^2 – 8xy – 4x + 4y b. x^3 + 10x^2 + 25x – xy^2 c. x^2 + x – 6 d. 2x^2 +

Toán Lớp 8: Câu 1 (2 điểm) Phân tích đa thức thành nhân tử
a. 8x^2 – 8xy – 4x + 4y b. x^3 + 10x^2 + 25x – xy^2
c. x^2 + x – 6 d. 2x^2 + 4x – 16
Câu 2 (2 điểm) Tìm giá trị của x, biết:
a. x^3 – 16x = 0 b. (2x + 1)^2 – (x – 1)^2 = 0

Comments ( 2 )

  1. Câu 1 : 
    a)8x^2-8xy-4x+4y
    = 8x(x – y)- 4(x – y)
    =(x – y)(8x – 4)
    = 4(x – y)(2x – 1)
    b)x^3+10x^2+25x-xy^2
    =x(x^2+10+25-y^2
    =x[(x-5)^2-y^2]
    =x(x-5-y)(x-5+y)
    c)x^2+x-6
    =x^2-2x+3x-6
    =x(x – 2) + 3(x – 2)
    =(x – 2)(x + 3)
    d)2x^2+4x-16
    =2(x^2-2x-8)
    =2(x^2-2x+1-3^2)
    =2[(x-1)^2-3^2]
    =2(x – 1 – 3)(x – 1 + 3)
    =2(x – 4)(x + 3)
    Câu 2 : 
    a)x^3-16x=0
    =>x(x^2-16)=0
    =>x(x – 4)(x + 4)=0
    =>$\left[\begin{matrix} x=0=1\\ x-4=0\\x+4=0\end{matrix}\right.$
    =>$\left[\begin{matrix} x=0\\ x=4\\x=-4\end{matrix}\right.$
    Vậy S={0; 4; -4}
    b)(2x + 1)^3-(x -1)^2=0
    =>(2x + 1 – x + 1)(2x + 1 + x – 1)=0
    =>(x + 2)(3x)=0
    =>$\left[\begin{matrix} x+2=0\\ 3x=0\end{matrix}\right.$
    =>$\left[\begin{matrix} x=-2\\ x=0\end{matrix}\right.$
    Vậy S={-2; 0}
     

  2. \text{Câu 1}
    a, 8x^2 – 8xy – 4x +4y
    = 8x( x-y) – 4(x-y)
    = (x-y)(8x-4)
    = 4(x-y)(2x-1)
    b, x^3 + 10x^2 + 25x – xy^2
    = x( x^2 + 10x + 25 -y^2 )
    = x [( x+5)^2 – y^2]
    = x( x+5-y)(x+5+y)
    c, x^2 + x-6
    = x^2 – 2x + 3x -6
    = x(x-2) + 3(x-2)
    =(x-2)(x+3)
    d, 2x^2 + 4x -16
    = 2(x^2 + 2x -8)
    = 2[( x^2 + 2x +1)-1 -8]
    = 2[(x+1)^2 – 9]
    = 2(x+1-3)(x+1+3)
    =2(x-2)(x+4)
    \text{Bài 2}
    a, x^3 – 16x=0
    x(x^2 – 16)=0
    x(x+4)(x-4)=0
    =>\(\left[ \begin{array}{l}x=0\\x=-4 \\ x=4\end{array} \right.\) 
    b, (2x+1)^2 – (x-1)^2 =0
    => ( 2x +1 + x -1)(2x+1-x+1)=0
    => 3x(x+2)=0
    =>\(\left[ \begin{array}{l}3x=0\\x+2=0\end{array} \right.\) 
    =>\(\left[ \begin{array}{l}x=0\\x=-2\end{array} \right.\) 

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