下列变形错误的是( )
A:4x – 5 = 3x+2变形得4x–3x = 2+5
B:3x–1 =' 2x+3' 变形得3x-2x = 3+1
C:23x – 1 = 12x+3变形得4x–1 = 3x+18
D:3x = 2变形得x =23
菱形ABCD的周长为16,∠A=60°,则BD的长为( )
如图有机物分子中带“*”碳原子是手性碳原子(连有四个不同基团的碳原子)。该有机物分别发生下列反应,生成的有机物分子中不会含有手性碳原子的是①与甲酸发生酯化反应 ②与足量NaOH水溶液反应③与银氨溶液作用只发生银镜反应 ④催化剂作用下与H2反应
根据句意和首字母提示,完成句中所缺单词①We should brush our____ (tooth) every day.②—What’s Jane doing? —She’s b____ her sister.③ What is she doing for v____ ?④—How do you come to school? —I usually ride a b____ to school.⑤ I want to s ____ an e-mail to my aunt.
如图,在△ABC中,点E、D、F分别在边AB、BC、CA上,且DE∥CA,DF∥BA.下列四个判断中,不正确的是( )