1. 3(a-6)=3a-18
2. (3a-18)a=3a^2-18a
3. (a-9)^2=a^2-18a+814. 3a^2-18a-(a^2-18a-81)=3a^2-18a-a^2+18a-81
5. 3a^2-a^2=2a^2
6. -18a+18a=0
1. 3(a-6)=3a-18
2. (3a-18)a=3a^2-18a
3. (a-9)^2=a^2-18a+81
4. 3a^2-18a-(a^2-18a-81)=3a^2-18a-a^2+18a-81
5. 3a^2-a^2=2a^2
6. -18a+18a=0