Question 1206638
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Only a person,  who does not know a subject,  may teach in a way as  @MathLover1 does it.


Her method to solve this problem is a classic example on how a student  SHOULD  NOT  do it.



In that sense,  it is very good that she posted her solution,


because it is good case and good opportunity for me to tell you :   NEVER  do it this way  ( ! )