题目

A primary school in Jinhua, Zhejiang Province has announced it no longer requires parents to sign their children’s homework, which was aimed at getting parents to supervise(监督) their children after school. China Youth Daily comments: Putting an end to the requirement that parents sign off on the homework of their children eases the burden on many parents, as otherwise they would have to do primary school homework after a hard day’s work. But there are worries that if parents stop having to sign off on their children’s homework, the children will not get good grades.However, the most 已知a是5的整数部分，b是5的小数部分，则a（b-5）=______．