Вправи 1201 - 1300 » 1276 (4-5)

4) –3/7 (2,1х + 42/3у) + 2,2 (–3/11х – 5/22у) = –0,9х – 2у – 0,6х – 0,5у = –1,5х – 2,5у. Якщо х = –11/3, у = 1,2, то –1,5х – 2,5у = –11/2 ∙ (–11/3) – 21/2 ∙ 6/5 = 3/2 ∙ 4/3 – 5/2 ∙ 6/5 = 2 – 3 = –1. 5) 7/23 (32/7а – 24/21b) – 9/16(51/3a – 8/15b) = 7/23(23/7a – 46/21b) – 9/16(16/3a – 8/15b) = a – 2/3b – 3a + 3/10b = –2a – 11/30b. Якщо а = 5,5, b = 28/11, то –2а – 11/30b = –2 ∙ 5,5 – 11/30 ∙ 28/11 = –11 – 11/30 ∙ 30/11 = –11 – 1 = –12.