Fusion

I still remember my math class at school. My teacher often wrote down a long expression with many alphabetic symbols in the blackboard, then asked the class to simplify it. Some student volunteered to do it in front of the class. Merged terms, factorized, …varies of tricks. It is like a magic process that often led to unbelievable simple result. Sometimes the guy was stuck or trapped in loops and finally saved by my teacher. Chalk and blackboard, such experience was unforgettable, just like it happened yesterday.