已知a+b=3,ab=1/2 a²b+2a²b²+ab² =(a²b+ab²)+2a²b² =ab(a+b)+2(ab)² =(-1/2)X3+2X(-1/2)² =-3/2+1/2 =-1,7,题目最好更新一下，看不明白,0,
