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

Toán Lớp 8: Rút gọn biểu thức: c, (5x-3).(4x-7) d, `2x . (x+1) – (x+2)^2`

Toán Lớp 8: Rút gọn biểu thức:
c, (5x-3).(4x-7)
d, 2x . (x+1) – (x+2)^2

Comments ( 2 )

  1. c/ (5x – 3) . (4x – 7)
    = 20x² – 35x – 12x + 21
    = 20x² – 47x + 21
    d/ 2x . (x + 1) – (x + 2)²
    = 2x² + 2x – (x² + 4x + 4)
    = 2x² + 2x – x² – 4x – 4
    = 2x² – x² + 2x – 4x – 4
    = x² – 2x – 4

  2. c/
    (5x-3)(4x-7)  
    = 20x^2 – 35x – 12x +21
    = 20x^2 -47x +21
    d/
    2x(x+1) -(x+2)^2
    = 2x^2 + 2x – (x^2 + 4x +4)
    = 2x^2 +2x -x^2-4x -4
    = x^2 -2 x -4 
     

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