The phrase "study at extend" can be expressed using a variety of synonyms that capture the essence of studying extensively. Some potential options include "research in depth," "analyze thoroughly," "investigate exhaustively," "delve deeply," and "explore extensively." Each of these phrases conveys a sense of comprehensive analysis and inquiry, emphasizing the importance of long-term focus and sustained effort. Other possibilities might include "probe extensively," "scrutinize closely," "examine minutely," or "pursue relentlessly," all of which highlight the need for persistence and dedication when it comes to mastering a subject or topic. Ultimately, the best synonym for "study at extend" will depend on the context and the specific nuances of the situation at hand.