Question

1) (14y+21)(1.8-0.3y)=0 2) 2(4x+1)-x=7x+3

Answer 1

1.
(14y + 21) = 0, или  (1.8 - 0.3y) = 0
1) 14y + 21 = 0
    14y = -21
    y = -1.5
2) 1.8 - 0.3y = 0
    18 - 3y = 0
    -3y = -18
    y = 6
Ответ: y1 = -1.5;
y2 = 6.

2.
2(4x - 1) - x = 7x + 3;
8x + 2 - x = 7x + 3;
8x - x - 7x = 3 - 2;
0 ≠ 1 = > (корней нет).