See also: に・1
emphasises word marked by に
to, for, on, in, at Expression
in order to Expression
See also: は・1
indicates respect for subject of sentence
as for, regarding Expression
as ＡにはＡが...; emphasizes the repeated word, followed by a contrasting statement
while it is (was) the case that ..., indeed ... (but), certainly ... (but)
Your personal translations
Mathematics is difficult for me. Math is hard for me.
One should take care of oneself. You should take care of yourself.
Takeshi did come, but didn't stay long.
I have not the least interest in detective stories.