"I must do my homework seriously" 可以用英文表达为 "I must take my homework seriously."
"Seriously" 是一个副词，意思是“认真地”，“严肃地”。"Take" 是一个动词，意思是“对待”, “处理”。
例句：
I must take my studies seriously if I want to be successful.
He took the job interview seriously and made a good impression on the employer.
中文翻译：
我如果想成功就必须认真对待我的学习。
他认真对待了面试，给雇主留下了很好的印象。