Математика 5 класс учебник Никольский, Потапов ответы – номер 852

а) 1/5 + 8/25 + 7/25 = 1/5 + (8/25 + 7/25) = 1/5 + ̶1̶5̶ ³/̶2̶5̶ ⁵ = 1/5 + 3/5 = 1/5 + 3/5 = 4/5; б) 1/7 + 2/21 + 3/7 = (1/7 + 3/7) + 2/21 = 4⁽³/7 + 2/21 = 12/21 + 2/21 = 14/21 = 2/3; в) 1/15 + 2/45 + 7/15 = (1/15 + 7/15) + 2/45 = 8⁽³/15 + 2/45 = 24/45 + 2/45 = 26/45; г) 3/49 + 5/7 + 4/49 = (3/49 + 4/49) + 5/7 = ̶7̶ ̶¹/̶4̶9̶ ⁷ + 5/7 = 1/7 + 5/7 = 6/7; д) 7/10 + 2/15 + 11/30 = 21 + 4 + 11/30 = 36/30 = 6/5; е) 1/12 + 1/18 + 1/12 = (1/12 + 1/12) + 1/18 = ̶2̶ ¹/̶1̶2̶ ⁶ + 1/18 = 1⁽³/6 + 1/18 = 3/18 + 1/18 = 4/18 = 2/9.