Prove that if \[\lim_{x\to a}\,f(x)=L,\] then \[\lim_{h\to 0}\,f(a+h)=L.\]

Problem: 

Prove that if \[\lim_{x\to a}\,f(x)=L,\] then \[\lim_{h\to 0}\,f(a+h)=L.\]

Answer: 

It is true that \[\mbox{if }\lim_{x\to a}\,f(x)=L\mbox{ then }\lim_{h\to 0}\,f(a+h)=L.\]