Question

you’d better put it in use at once

you’d better put it in use at once

Answer 1

had better是一个情态动词的词组，后面跟动词原形，其否定式是把not加在had better的后面，意思是“最好”。
had better 是“最好”的意思，可将其视为“情态”动词，可用于一切人称，没有任何词形变化。它的基本特点是： 1、其后接不带to的不定式，表示现在或将来的概念，如： You had better sit here and have a rest. 你最好在此坐坐休息一会儿。（现在） He had better stay in bed tomorrow. 他最好明天卧床休息。（将来）。 2、当其后接 have + 过去分词时，表示过去概念，如： He had better have stayed in bed as I suggested.
希望我能帮助你解疑释惑。

Answer 2

你最好马上加以应用。

Answer 3

you’d better put it in use at once
你最好马上用它