Đáp án:
\(60n+45\ \vdots\,\,\,\,\,15\)
\(60n+45\ \not {\vdots}\,\,\,\,\,30\)
Giải thích các bước giải:
Ta có:
\(60n+45=15.4n+15.3=15.(4n+3)\ \vdots\,\,\,\,\,15\)
\(60n+45=30.2n+30+15=30.(2n+1)+15\ \not{\vdots}\,\,\,\,\,30\) (\(15\ \not{\vdots}\,\,\,\,\,30\))