搜题请搜索小程序“爱下问搜题”
问题 选择题
运算符号△的含义是a△b=
a，a≥b
b，a＜b
，则方程（1+x）△（1-2x）=5的所有根之和为（　　）
A．-2B．0C．2D．4
答案

当x≥0时，1+x≥1-2x，

∴1+x=5，解得x=4；

当x＜0时，1+x＜1-2x，

∴1-2x=5，解得x=-2．

所以方程（1+x）△（1-2x）=5的所有根之和为4+（-2）=2．

故选C．

选择题

1gN2中含有x个原子，则阿伏加德罗常数是

A．（x/28）mol-1

B．（x/14）mol-1

C．14x mol-1

D．28x mol-1
查看答案
单项选择题 共用题干题

Software architecture reconstruction is an interpretive, interactive, and iterative process including many activities. (1) involves analyzing a system's existing design and implementation artifacts to construct a model of it. The result is used in the following activities to construct a view of the system. The database construction activity converts the (2) contained in the view into a standard format for storage in a database. The (3) activity involves defining and manipulating the information stored in database to reconcile, augment, and establish connections between the elements. Reconstruction consists of two primary activities: (4) and (5). The former provides a mechanism for the user to manipulate architectural elements, and the latter provides facilities for architecture reconstruction.

空白（2）处应选择（）

A.actors and usecases

B.processes and data

C.elements and relations

D.schemas and tables
查看答案