Question 702931
Call the endpoints ( -3,2 ), and ( x1, y1 )
The mid-point is ( -1,5 )
Treat the x and y coordinates separately
{{{ ( -3 + x[1] ) / 2 = -1 }}}
{{{ -3 + x[1] = -2 }}}
{{{ x[1] = 1 }}}
and
{{{ ( 2 + y[1] ) / 2 = 5 }}}
{{{ 2 + y[1] = 10 }}}
{{{ y[1] = 8 }}}
The coordinates of B are ( 1,8 )
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check:
{{{ ( 1 +(-3) ) / 2 = -1 }}}
and
{{{ ( 8 + 2 ) / 2 = 5 }}}
The midpoint is ( -1,5 ) 
OK