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

Toán Lớp 7: 1) 5 (2x+3) ( x+2) -2 ( 5x-4) (x-1) 2) (10x+9) x- (5x-1) (2x+3) 3) 3 (2x-1) -5 (x-3)+6 ( 3x-4)

Toán Lớp 7: 1) 5 (2x+3) ( x+2) -2 ( 5x-4) (x-1)
2) (10x+9) x- (5x-1) (2x+3)
3) 3 (2x-1) -5 (x-3)+6 ( 3x-4)

Comments ( 2 )

  1. a)
    5(2x+3)( x+2) -2 ( 5x-4) (x-1)
    =10x(x + 2) + 15(x+2) – 2(5x-2)(x-1)
    = 10x^2 + 20x + 15(x+2) – 2(5x-2)(x-1)
    = 10x^2 + 20x + 15x + 30 -2(5x-2)(x-1)
    = 10x^2 + 35x + 30 -2(5x-2)(x-1)
    = 10x^2 + 35x + 30 -10x(x-1)+8(x-1)
    = 10x^2 + 35x + 30 -10x^2 + 10x +8x-8
    = (10x^2 – 10x^2) + (35x + 10x + 8x) + ( 30 – 8)
    = 53x + 22
    b)
    (10x+9) x- (5x-1) (2x+3)
    = 10x^2 + 9x – (5x-1) (2x+3)
    = 10x^2 + 9x – [5x(2x+3) – 1(2x+3)]
    = 10x^2 + 9x – [10x^2 + 15x -( 2x + 3)]
    = 10x^2 + 9x – (10x^2 + 15x – 2x – 3)
    = 10x^2 + 9x – [(10x^2 + (15x – 2x) – 3)]
    = 10x^2 + 9x – (10x^2 + 13x – 3)
    = 10x^2 + 9x – (10x^2 + 13x – 3)
    = 10x^2 + 9x – 10x^2 – 13x + 3
    = (10x^2 – 10x^2) + (9x – 13x) + 3
    = -4x + 3
    c)
    3 (2x-1) -5 (x-3)+6 ( 3x-4)
    = 6x – 3 – 5x + 15 + 18x – 24
    = 6x – (3+15-24) – 5x + 18x
    = 6x – 12 – 5x + 18x
    = (6x – 5x + 18x ) – 12
    = 19x – 12

  2. Giải đáp: + Lời giải và giải thích chi tiết:
    1)
    5(2x+3)(x+2)-2(5x-4)(x-1)
    = 10x^2 + 35x + 30 – 2(5x-4)(x-1)
    = 10x^2 + 35x + 30 – 10x^2 + 18x – 8
    = (10x^2-10x^2) + (35x+18x) + (30-8)
    = 53x + 22
    2)
    (10x+9)x-(5x-1)(2x+3)
    = 10x^2 + 9x – (5x-1)(2x+3)
    = 10x^2 + 9x – 10x^2 – 13x + 3
    = (10x^2-10x^2) – (13x-9x) + 3
    = -4x + 3
    3)
    3(2x-1)-5(x-3)+6(3x-4)
    = 6x – 3 – 5x + 15 + 6(3x-4)
    = 6x – 3 – 5x + 15 + 18x – 24
    = (18x+6x-5x) – (24-15+3)
    = 19x – 12

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