Question 201015
remember  midpoint  formula,  x = (x1+x2) /2,,,,,y  = (y1 +y2) /2
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use  4,5,6  to  remember,  while  we  can  do  (6-4) /2 =1,  and  4+1 =5,,,
it  also  works  if  we  do  4 +6 =10 /2 =5
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in  this  case,,x = { 5 +(-3) } /2 = +1
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y = { 2 + 8 } /2 = + 5
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Check,,,
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1+4 =5, 1-4 = -3,,,,,ok
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5+3 =8,,5-3 = 2  ,,,,,,ok