整式化简后求值题步骤尽量全一点麻烦各位了哈 悬赏暂时20分 满意答案可以给50哦

1.15a-{-4a+【5a-8a-（2a-a）+9a】-3a} =15a^2-[-4a^2+(5a-8a^2-2a^2+a+9a^2)-3a] =15a^2-(-4a+6a-a^2-3a) =15a^2-(-a^2-a) =15a^2+a^2+a =16a^2+a =16(-3/2)^2-3/2 =69/2 2.(1/2)(a-b)+3(2a-b)-(3a-b) =(1/2)a-(1/2)b+6a-3b-3a+b =(1/2+6-3)a-(1/2+3-1)b =(7/2)a-(5/2)b =7+5/2 =19/2 3.a=-2，b=-1，c=1/3 5abc-{2ab-[3abc-(4ab-ab]} =5ab-[2a^2b-(3abc-4ab^2+a^2b)] =5ab-(2a^2b-3abc+4ab^2-a^2b) =5ab-a^2b+3abc-4ab^2 =10+4+2+8 =24