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

Toán Lớp 8: Bài 1: Rút gọn: 1) (x + 2) (3x – 4) + (x – 3) ² 2) (x – 5) (x + 5) – (x + 5) ² 3) (4 – x) ² – (x – 3) ² 4) (x – 3) ² – (x – 4) (x + 4

Toán Lớp 8: Bài 1: Rút gọn:
1) (x + 2) (3x – 4) + (x – 3) ²
2) (x – 5) (x + 5) – (x + 5) ²
3) (4 – x) ² – (x – 3) ²
4) (x – 3) ² – (x – 4) (x + 4)
5) (2x + 3) ² – (x – 2) (x + 1)
6) (x + 5) ³ – 15 (x + 10)
7) (x – 2) ³ – (a – 5) ²
8) (x + 2) (x ² – 2x + 4) – (x ³ + 8)
9) (x – 3) (x ² + 3x + 9) – (x ² – 1) (x + 27)

Comments ( 1 )

  1. 1) (x + 2) (3x – 4) + (x – 3) ²
    = 3x² – 4x + 6x – 8 + x² – 6x + 9
    = 4x² – 4x + 1
    2) (x – 5) (x + 5) – (x + 5) ²
    = (x + 5) (x – 5 – x – 5)
    = -10 (x + 5)
    3) (4 – x) ² – (x – 3) ²
    = 8x² – 8x + x² – x² + 6x – 9
    = 8x² – 2x – 9
    4) (x – 3) ² – (x – 4) (x + 4)
    = x² – 6x + 9 – x² + 16
    = -6x + 25
    5) (2x + 3) ² – (x – 2) (x + 1)
    = 4x² +  12x + 9 – (x² + x – 2x – 2)
    = 4x² +  12x + 9 – x² – x + 2x + 2
    = 3x² + 13x + 11
    6) (x + 5) ³ – 15x (x + 10)
    = x³ + 15x² + 75x + 125 – 15x² – 15
    = x³ + 75x + 110
    7) (x – 2) ³ – (x – 5) ²
    = x³ – 6x² + 12x – 8 – x² + 10x – 25
    = x³ – 7x² + 22x – 33
    8) (x + 2) (x ² – 2x + 4) – (x ³ + 8)
    = x³ + 8 – x³ – 8
    = 0
    9) (x – 3) (x ² + 3x + 9) – (x ² – 1) (x + 27)
    = x³ – 27 – (x³ + 27x² – x – 27)
    = x³ – 27 – x³ – 27x² + x  + 27
    = -27x² + x

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

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