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

Toán Lớp 8: rút gọn thành nhân tử (x^2+9)^2+8x(x^2+9)+12x^2

Toán Lớp 8: rút gọn thành nhân tử (x^2+9)^2+8x(x^2+9)+12x^2

Comments ( 2 )

  1. Giải đáp:
     (x^2 + 9)^2 + 8x(x^2 + 9) + 12x^2
    = (x^2 + 9)^2 + 8x(x^2 + 9) + 16x^2 – 4x^2
    = [(x^2 + 9)^2 + 2.(x^2 + 9).4x + (4x)^2] – 4x^2
    = (x^2 + 9 + 4x)^2 – (2x)^2
    = (x^2 + 9 + 4x + 2x)(x^2 + 9 + 4x – 2x)
    = (x^2 + 6x + 9)(x^2 + 2x + 9)
    = (x^2 + 2.x.3 + 3^2)(x^2 + 2x + 9)
    = (x + 3)^2 (x^2 + 2x + 9)
    * Áp dụng hằng đẳng thức:
    (A + B)^2 = A^2 + 2AB + B^2
    A^2 – B^2 = (A – B)(A + B)

  2. ***Lời giải***
    (x^2+9)^2+8x(x^2+9)+12x^2
    =[(x^2+9)^2+8x(x^2+9)+16x^2]-4x^2
    =[(x^2+9)^2+2.4x(x^2+9)+(4x)^2]-(2x)^2
    =(x^2+9+4x)^2-(2x)^2
    =(x^2+9+4x-2x)(x^2+9+4x+2x)
    =(x^2+2x+9)(x^2+6x+9)
    =(x^2+2x+9)(x^2+2.3x+3^2)
    =(x^2+2x+9)(x+3)^2

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

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