N1
а) 8/5 + 3/4 = 32/20 + 15/20 = 47/20
б) - 11/12 + 11/20 = - 55/60 + 33/60 = - 22/60 = - 11/30
в) 8/9 - 8/15 = 40/45 - 24/45 = 16/45
г) 7/16 - ( - 11/12 ) = 7/16 + 11/12 = 65/48
д) - 14/21 + ( - 15/28) = - 14/21 - 15/28 = - 101/84
N2
а) 3/xy + 10/xy = 3/xy + 10/xy = 13/xy
б) a/ a - b = 1 - b
в) 12x / x² - 8x/ x² + 1 = 12x/x² - 8x/x² = 12/x - 8/x = 4/x