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

Toán Lớp 8: 1)x^2+6x+9 2)10x-25-x^2 3)8x^3-1/8 4)1/25x^2 -64y^2

Toán Lớp 8: 1)x^2+6x+9
2)10x-25-x^2
3)8x^3-1/8
4)1/25x^2 -64y^2

Comments ( 2 )

  1. Giải đáp:
     
    Lời giải và giải thích chi tiết:
    x^2+6x+9
    =(x+3)^2
    _________________________________
    10x-25-x^2
    =-(x^2-10x+25)
    =-(x-5)^2
    ____________________________________
    8x^3-1/8
    =(2x-1/2)(4x^2+x+1/4)
    ____________________________________
    1/25x^2-64y^2
    =(1/5x-8y)(1/5x+8y)

  2. 1) x^2 + 6x + 9
     = x^2 + 2.3x + 3^2
     = (x+3)^2
    2) 10x – 25 – x^2
     = – (x^2 – 10x + 25)
     = – (x^2 – 2.5x + 5^2)
     = – (x-5)^2
    3) 8x^3 – 1/8
      = (2x)^3 – (1/2)^3
      = (2x – 1/2 )(4x^2 + x + 1/4)
    4) 1/25x^2 – 64y^2
      = (1/5x)^2 – (8y)^2
      = (1/5x – 8y)(1/5x+8y)  

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

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