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

Toán Lớp 8: Phân tích đa thức sau thành nhân tử: `x^3−6x^2−x+30`

Toán Lớp 8: Phân tích đa thức sau thành nhân tử:
x^3−6x^2−x+30

Comments ( 2 )

  1. x^3-6x^2-x+30 
    =x^3+2x^2-8x^2-16x+15x+30
    =x^2(x+2)-8x(x+2)+15(x+2)
    =(x^2-8x+15)(x+2)
    =(x^2-5x-3x+15)(x+2)
    =[x(x-5)-3(x-5)](x+2)
    =(x-3)(x-5)(x+2)

  2. x^3 – 6x^2 – x + 30
    = x^3 – 8x^2 + 2x^2 + 15x – 16x + 30
    = (x^3+2x^2) – (8x^2+16x) + (15x+30)
    = x^2 (x+2) – 8x (x+2) + 15 (x+2)
    = (x+2) (x^2-8x+15)
    = (x+2) (x^2 -3x-5x+15)
    = (x+2) [x(x-3)-5(x-3)]
    = (x+2) (x-3) (x-5)
     

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