① ____ A. I have a shirt.
② ____ B. I like running.
③ ____ C. It is green.
gāo tang áo suàn shòu què
熬____ 糕____ 糖____ 确____ 算____ 售____
选修4-5:不等式选讲
已知函数f(x)=|x+1|-2|x-a|, a>0.