【1】[5a^2-2ab]-2[3a^2+4ab-2分之1b^2]
= 5a^2-2ab-6a^2-8ab+b^2
= 5a^2-6a^2-2ab-8ab+b^2
= -a^2-10ab+b^2
【2】[4ab^2+2分之3a^3]-{2分之1a^2b+[5ab^2+2分之5a^3]+5a^3}+2分之1a^2b
=4ab^2+2分之3a^3-{2分之1a^2b+5ab^2+2分之5a^3+5a^3}+2分之1a^2b
=4ab^2+2分之3a^3-{2分之1a^2b+5ab^2+2分之15a^3}+2分之1a^2b
=4ab^2+2分之3a^3-2分之1a^2b-5ab^2-2分之15a^3+2分之1a^2b
=4ab^2-5ab^2+2分之1a^2b-2分之1a^2b+2分之3a^3-2分之15a^3
=-ab^2b-6a^3
【3】9a^2+[7a^2-2a-[a^2-3a]-a^2]+4a
=9a^2+[7a^2-2a-a^2+3a-a^2]+4a
=9a^2+[7a^2-a^2-a^2-2a+3a]+4a
=9a^2+[5a^2+a]+4a
=9a^2+5a^2+a+4a
=14a^2+5a