`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))`