Question 1181173
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When students come to the forum with such problems,  they should learn  THE  LOGIC  of the solution,

and that is all what they should know.



The students should not know these formulas,  that  @josgarithmetic tries to sell you.



Even do not try to understand or memorize these formulas --- keeping them in your mind is absolutely useless

and will teach you to NOTHING.



THEREFORE,  for a sake of your safety,  ignore his post and do not load this  TRASH  into your head / (mind).



May god saves you from it . . . 



Keep your mind clean for more useful/vital tasks of your life.