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

Toán Lớp 8: dễ lém phân tích đa thức thành nhân tử: a, 6x²+13x+5 b, 15x²+11x-12 c, x³-x²+2 d, x³-4x²+x+6

Toán Lớp 8: dễ lém
phân tích đa thức thành nhân tử:
a, 6x²+13x+5
b, 15x²+11x-12
c, x³-x²+2
d, x³-4x²+x+6

Comments ( 2 )

  1. a) 6x^2+3x+10x+5

    =3x(2x+1)+5(2x+1)

    =(3x+5)(2x+1)

    b) 15x^2+11x-12

    =15x^2+20x-9x-12

    =5x(3x+4)-3(3x+4)

    =(5x-3)(3x+4)

    c) x^3-x^2+2

    =x^3+x^2-2x^2+2

    =x^2(x+1)-2(x^2-1)

    =x^2(x+1)-2(x-1)(x+1)

    =(x+1)[x^2-2(x-1)]

    =(x+1)(x^2-2x+2)

     

  2. a,6x^2+13x+5
    =(6x^2+10x)+(3x+5)
    =2x(3x+5)+(3x+5)
    =(3x+5)(2x+1)
    b,15x^2+11x-12
    =(15x^2+20x)-(9x+12)
    =5x(3x+4)-3(3x+4)
    =(3x+4)(5x-3)
    c,x^3-x^2+2
    =(x^3+x^2)+(-2x^2+2)
    =x^2(x+1)-2(-x^2+1)
    =x^2(x+1)+2(1-x^2)
    =x^2(x+1)+2(1-x)(1+x)
    =(x+1)[x^2+2(1-x)]
    =(x+1)(x^2+2-2x)
    d,x^3-4x^2+x+6
    =(x^3+x^2)-(5x^2+5x)+(6x+6)
    =x^2(x+1)-5x(x+1)+6(x+1)
    =(x+1)(x^2-5x+6)
    =(x+1)[(x^2-2x)-(3x-6)]
    =(x+1)[x(x-2)-3(x-2)]
    =(x+1)[(x-2)(x-3)]
    =(x+1)(x-2)(x-3)

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