Вправи: 319

319. Розв’яжіть рівняння

а) 2(х – 3) + 5(х – 2) = 12; 2х – 6 + 5х – 10 = 12; 7x – 16 = 12;

7x = 28; х = 4;

б) 3(1 – x) – 2(3 – x) = 5; 3 – Зx – 6 + 2x = 5; –x – 3 = 5; –x = 8;

x = – 8;

в) Зz – 7(2z + 4) = 18; Зz – 14z – 28 = 18; –11z = 18 + 28;

–11z = 46; z = –4,(18); z = –211;

г) 2 + 3у – 7(5– у) = 15; 2 + Зy – 35 + 7y = 15; 10у – 33 = 15;

10y = 48; у = 4,8.

ґ) x² – 3x + 1 = х(х + 2); x² – Зх – x² – 2х = –1; –5x = –1; x = 15;

д) 0,7x + 0,5 = 2,6(x – 2); 0,7x + 0,5 = 2,6x – 5,2;

0,7x – 2,6x = –5,2 – 0,5; –1,9x = –4,7; x = 4719; x = 2919;