решите уравнения:1) (7х-5)х=(1,5-2.1х)2) (1-8х)х=(11,2х-1,4)3) (1,7х-1/3)х=(3-15,3х)*1/24)

1) (7х-5)х=(1,5-2.1х); 7х-5х = 1,5 - 2.1х 10; 70х- 50х = 15 - 21х; 70х- 29х - 15 = 0;

D = 29 + 47015 = 841 + 4200 = 5041; D = 71; x = (29 + 71)/140 = 100/140=5/7;

x = (29 - 71)/140 = 42/140=3/20 = 0.15. Ответ: 5/7; 0,15.

2) (1 - 8х)х=(11,2х - 1,4); x - 8х = 11,2х - 1,45; 5x - 40х = 56х - 7; 40х + 51x - 7 = 0; D = 51 + 1120 = 2601 + 1120 = 3721; D = 61; x = (-51 + 61)/80 = 10/80= 1/8 = 0,125; x = (-51 - 61)/80 = -111/80= -1,3785. Ответ: 0,125; -1,3785.

3) (1,7х - 1/3)х=(3 - 15,3х)*1/2; 1,7х - (1/3)х = (3 - 15,3х)*1/260; 102х -20х = (30 - 153х)*3; 102х -20х = 90 - 459х; 102х +439х - 90 = 0; D = 439 + 360102 = 229441; D = 479; x = (-439+ 479)/204 = 40/204 = 10/51; x =(-439 - 479)/204 = -918/204 = -459/102 = -153/34 = -9/2 = -4,5. Ответ: 10/51; -4,5.

4) (х/7 - 1(6/7))х=(3,9-0,3х)*1/35350; 50x - 650x = 39 - 3x; 50x - 647x - 39 = 0; D = 418609 + 20039 = 426409; D = 653; x = (650 + 653)/100 = 13,03; x = (650 - 653)/100 = - 0,03. Ответ: 13,03; - 0,03.