下列式子中代数式的个数有( )
﹣2a﹣5,﹣3,2a+1=4,3x3+2x2y4,﹣b.
2﹣甲基﹣1,3﹣丁二烯与溴发生加成反应时能得到几种产物?请写出它们的结构简式.
—I have no idea ____________ tell her the bad news. —I think tomorrow is the best time.
如果x+y=6x-(m-1)y=9中的解x、y相同,则m的值是( )