1). Сделайте деяния: а) 1,6 (4,5); б) -1 целая 7/8*(-1

1) а) 1,6 * (- 4,5) = - 1,6 * 4,5 = - 16/10 * 45/10 = - 8/5 * 9/2 = - (8 * 9)/(5 * 2) = - 72/10 = - 7,2;

б) - 1 7/8 * (- 1 1/3) = 1 7/8 * 1 1/3 = 15/8 * 4/3 = (15 * 4)/(8 * 3) = (5 * 1)/(2 * 1) = 5/2 = 2 1/2;

в) - 135,2 : (- 6,5) = 135,2 : 6,5 = 1352/10 : 65/10 = 1352/10 * 10/65 = 1352/65 = 20 52/65;

г) - 1 2/3 : 3 1/3 = - 5/3 : 10/3 = - 5/3 * 3/10 = - 5/10 = - 1/2.

2) (- 9,18 : 3,4 - 3,7) * 2,1 + 2,04 = - 11,4.

1. - 918/100 : 34/10 = - 918/100 * 10/34 = - (918 * 10)/(100 * 34) = - (27 * 1)/(10 * 1) = - 27/10;

2. - 27/10 - 3,7 = - (27/10 + 37/10) = - 64/10;

3. - 64/10 * 2,1 = - 64/10 * 21/10 = - (64 * 21)/(10 * 10) = - (32 * 21)/(5 * 10) = - (16 * 21)/(5 * 5) = - 336/25;

4. - 336/25 + 2,04 = - (336/25 - 204/100) = - (336 * 4 - 204)/100 = - 1140/100 = - 11 40/100 = - 11,4.  

4) 3/7 * (- 0,54) - 3/75 = - 3/7 * 54/100 - 3/75 = - (3 * 54)/(7 * 100) - 3/75 = - (162/700 + 3/75) = - (162/700 + 1/25) = - (162 + 28)/700 = - 190/700 = - 19/70. 

5) (6х - 9)(4х + 0,4) = 0;

6x - 9 = 0 либо 4x + 0,4 = 0;

6x = 9;

x = 9/6 = 3/2 = 1 1/2.

4x = - 0,4;

x = - 0,4 : 4 = - 4/10 * 1/4 = - 1/10 = - 0,1.

Ответ: х = 1 1/2 или х = - 0,1.