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

Toán Lớp 8: thực hiện phép tính a, x^2-2/x^2-4x + 3x/x-4 + 7/5x b, 6/x^2-3x+2 + 2x-2/x^2-4

Toán Lớp 8: thực hiện phép tính
a, x^2-2/x^2-4x + 3x/x-4 + 7/5x
b, 6/x^2-3x+2 + 2x-2/x^2-4

Comments ( 1 )

  1. a) (x^2 – 2)/(x^2 – 4x) + (3x)/(x – 4) + 7/(5x)
    ĐKXĐ: x ne 0; 4
    = (5(x^2 – 2))/(5x(x – 4)) + (5x. 3x)/(5x(x – 4)) + (7(x – 4))/(5x(x – 4))
    = (5x^2 – 10)/(5x(x – 4)) + (15x^2)/(5x(x – 4)) + (7x – 28)/(x – 4)
    = (5x^2 – 10 + 15x^2 + 7x – 28)/(5x(x – 4)
    = (20x^2 + 7x – 38)/(5x(x – 4))
    b) 6/(x^2 – 3x + 2) + (2x – 2)/(x^2 – 4)
    ĐKXĐ: x ne 1; 2; -2
    = 6/((x – 2)(x – 1)) + (2(x – 1))/((x – 2)(x + 2))
    = (6(x + 2))/((x – 1)(x + 2)(x – 2)) + (2(x – 1)^2)/((x – 1)(x + 2)(x – 2))
    = (6(x + 2) + 2(x – 1)^2)/((x – 1)(x + 2)(x – 2))
    = (6x + 12 + 2(x^2 – 2x + 1))/((x – 1)(x + 2)(x – 2))
    = (6x + 12 + 2x^2 – 4x + 2)/((x – 1)(x + 2)(x – 2))
    = (2x^2 + 2x + 14)/((x – 1)(x + 2)(x – 2))

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