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

Toán Lớp 8: B=2x*(3x^2-5x+8)-3x^2*(2x-5)-16x vs x=15 giúp em mn ơi

Toán Lớp 8: B=2x*(3x^2-5x+8)-3x^2*(2x-5)-16x vs x=15
giúp em mn ơi

Comments ( 2 )

  1. B=2x(3x^2-5x+8)-3x^2(2x-5)-16x với  x=-15 
    B=2x(3x^2-5x+8)-3x^2(2x-5)-16x
    B= 6x^3 – 10x^2 + 16x – 6x^3 + 15x^2 – 16x
    B= (6x^3 – 6x^3) + (-10x^2 + 15x^2) + (16x – 16x)
    B = 5x^2
    Thay x = -15 vào B, ta được:
    B = 5.(-15)^2
    B = 5.225
    B = 1125 

  2. B = 2x(3x^2 – 5x + 8) – 3x^2(2x – 5) – 16x
    B = 6x^3 – 10x^2 + 16x – 6x^3 + 15x^2 – 16x
    B = 5x^2
    Với  x = -15
    ⇒ B = 5 . (-15)^2
    B = 5 . 225
    B = 1225

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

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