ln（1+x^2）/secx-cosx的极限怎么求?

解方程（2/x²+x）+（3/ 解方程x/（x-2）-1=1/x 解方程120%x+1.8=1.2 2:120=x：8解方程 24÷120+X=8%解方程 （x-120)(70-x+130)=16 方程：X+4分之1=12分之11=?9分 （有补充!）直接写出得数（1）18分之7 4.4x+5.5x=99　　（解方程） who is already in her fifties who is an English teacher?应该怎么回答 who is arms longer your or my who is dancing ? Mary does. Who is doing sth who is doing sth.?回答