I have written a solution of problem in LYX. I exported the lyx code as latex plain code. I opened the latex plain code in Tex studio and copied it and pasted it in Physics forum and it didn't work. Can anyone please tell me what should I do? Should I again type the latex code here i.e.Physics Forum? I am attaching the Latex code and corresponding pdf. The tex file is not accepted here.So, attaching images.