（-5a2+4b2）（ ）=25a4-16b4，括号内应填（ ） A．5a2+4 发布时间：2017-05-13 12:39 │ 来源：www.tikuol.com 题型：选择题 问题： （-5a2+4b2）（ ）=25a4-16b4，括号内应填（ ）A．5a2+4b2B．5a2-4b2C．-5a2-4b2D．-5a2+4b2
题型：选择题 With so many difficult problems _____, the newly-elected president, Obama, is to have a hard time.A. settledB. settling C. to settle D. being settled 查看答案