Question 1199403
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This problem invites to find an error in the somebodies' incorrect calculations.


As a rule, such problems teaches  NOTHING  and are used by incompetent teachers simply to kill 

the time during a lesson,  when such  "teachers"  don't know how to use this time productively.


From the very beginning you make non-equivalent  " prohibited "  transformations,
and then make  " blue eyes "  and ask what is wrong.


As I said,  such problems do teach  NOTHING  and only serve to kill the time.



Run from the teachers who give such assignments,  as fast and as far as you can.