题目

阅读理解 According to a new US study, coupleswho expect their children to help care for them in old age should hope theyhave daughters because they are likely to be twice as attentive overall. The research by Angelina Grigoryeva, asociologist at Princeton University, found that, while women provide as muchcare for their elderly parents as they can manage, men do as little as they canget away with and often leave it to female family members. Using data from the University of MichiganHealth and Retirement Study, a study which has been tracking a cross-section ofover-50s for the last decade, 若函数的图象是在二、四象限的双曲线，则m=_________．