To find my childhood friend

Lu xiuche walked up to the podium in a few steps, looking very confident. He picked up a piece of chalk and stood in front of the blackboard. He thought about something and began to write.

He remembered the steps that Yue tingfeng wrote down in his head, but he had to calculate every step on the blackboard himself. Otherwise, the teacher would be suspicious.

His math teacher was standing behind him, watching him write every step.

Lu xiuche took six to seven minutes to write the question. He put down the chalk after he was done and was about to go down when the teacher stopped him.

He was shocked. Could it be that the teacher had discovered something and felt that this wasn't something he could have thought of and was prepared to criticize him?