①根据y₁=2y₂，∴6-x=2×2+14x，解得：x=

2

15

．
②由y₁比y₂小-3，∴y₁-y₂=-3，∴6-x-2-7x=-3，解得：x=

1

8

．
③由y₁与y₂互为相反数，∴y₁+y₂=0，∴6-x+7x+2=0，解得：x=−

4

3

．