1.A ∪B={ 1，2，3，4 }；

2.A-B = { 2 }；

3. Domain name: 1

4.f( 1) because1>; 0, so f( 1)=4 times1+2 = 6;

5. {y = t power of e; T = arctangent √x (where t = arctangent √ x