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

Toán Lớp 8: phân tích đa thức sau thành nhân tử : a,x^2+8x+15 ; b ,x^2-x-12 ; c,x^2+4x+3 ; d, 4x^2+4x-3

Toán Lớp 8: phân tích đa thức sau thành nhân tử : a,x^2+8x+15 ; b ,x^2-x-12 ; c,x^2+4x+3 ; d, 4x^2+4x-3

Comments ( 2 )

  1. a) x²+8x+15
    =x²+3x+5x+15
    =x(x+3)+5(x+3)
    =(x+3).(x+5)
    b) x²-x-12
    =x²-4x+3x-12
    =x(x-4)+3(x-4)
    =(x+3).(x-4)
    c) x²+4x+3
    =x²+3x+x+3
    =x.(x+3)+(x+3)
    =(x+1).(x+3)
    d) 4.x²+4x-3
    =4.x²-2x+6x-3
    =2x.(2x-1)+3.(2x-1)
    =(2x+3).(2x-1)
     

  2. a) x^2 + 8x + 15
    = x^2 + 3x + 5x + 15
    = x(x + 3) + 5(x + 3)
    = (x + 3)(x + 5)
    b) x^2 – x – 12
    = x^2 – 4x + 3x – 12
    = x(x – 4) + 3(x – 4)
    = (x + 3)(x – 4)
    c) x^2 + 4x + 3
    = x^2 + 3x + x + 3
    = x(x + 3) + (x + 3)
    = (x + 1)(x + 3)
    d) 4x^2 + 4x – 3
    =4 . x^2 -2x + 6x – 3
    = 2x(2x – 1) + 3(2x-1)
    = (2x + 3)(2x – 1)

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

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