题目

One of the latest trends(趋势) in American childcare is Chinese au pairs.Au Pair in Stamford,Conn.,for example,has got increasing numbers of requests for Chinese au pairs from zero to around 4,000 since 2004.And that’s true all across the country. “I thought it would be very useful for him to learn Chinese at an early age,”Joseph Stocke,the managing director of a company,says of his 2-year-old son.“I would at least like to give him the chance to use the language in the future.”After only six months of being cared for by a 25-year-old woman from China,the boy can already unde已知函数f(x)=2x-12x+1，设a，b∈R，且f（a）+f（b-1）=0，则a+b=11．