Our Summer Camp
When
On July 5th
Where
A ____mountain village
Who
Stay with the____
What
In the morning, we'll learn to ____animals from the local people.
In the afternoon, we'll____about the river.
In the evening, we'll enjoy the bright____.
我国五个省级少数民族自治区主要少数民族是( )
等差数列{an}中,如果a1+a4+a7=39,a3+a6+a9=27,则数列{an}前9项的和S9=( )
一物体受到大小分别为F1、F2、F3的三个共点力的作用,其力的矢量关系如图所示,则它们的合力大小是( )