So: a? -a+ 1=3 or a
Solve the equation: a=- 1 or 2 or 1. Substitute a into the set and verify that a= 1 is invalid.
So a=- 1 or 2.
2: x-a < 0, so: x < a.
Because; A is indeed contained in B, so: X < A contains a range greater than 1 < X < 2 (it can be turned into a number axis).
So; a≥2
Question 3: For Scheme A, x= 1 or x=2,
Because: b is contained in a.
Therefore, if x= 1 or x=2 in set b is substituted into b, a= 1 or a=2 is obtained.
When b is an empty set:
△=4-4(a- 1) 2 (Thanks for scoring! )