Ответ:

1. -2.5

2. -0.2

3. 9.8

4. 0.39

5. -0.98

Объяснение:

1. 6/х-3/2х = 12/2х-3/2х = 9/2х

9/2*(-1.8) = 9/-3.6 = -2.5

2. 21/3а-а2-7/а = 21/а(3-а)-7(3-а)/а(3-а) = 21-21+7а/а(3-а) = -7/3-а

-7/35 = -0.2

3. b + 2a-b2/b = b2+2a-b2/b = 2a/b

98/10 = 9.8

4. 1/5а + 1/4а * а2/9 = 4/20а + 5/20а * а2/9 = а2/20а = а/20

7.8/20 = 0.39

5. xy+y2/45x * 9x/x+y = y(x+y)/45x * 9x/x+y = y/5

-4.9/5 = -0.98