YOU SAID:
Math is not a good thing, (in my opinion)
INTO JAPANESE
数学は(私の意見では)良いことではない
BACK INTO ENGLISH
Mathematics is not a good thing (in my opinion)
INTO JAPANESE
数学は(私の意見では)良いことではありません
BACK INTO ENGLISH
Mathematics is not a good thing (in my opinion)
That didn't even make that much sense in English.