Question 697381
You are looking for B( x,y ) which is
an endpoint.
The x-coordinate of  the mid-point is
defined as:
(1) {{{ ( x[A] + x[B] ) / 2 = x[M] }}}
The y-coordinate of the mid-point is
defined as:
(2) {{{ ( y[A] + y[B] ) / 2 = y[M] }}}
-------------------------
{{{ x[A] = 2 }}}
{{{ y[A] = -6 }}}
{{{ x[M] = 5 }}}
{{{ y[M] = -1 }}}
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Filling in the numbers:
(1) {{{ ( 2 + x[B] ) / 2 = 5 }}}
(2) {{{ ( -6 + y[B] ) / 2 = -1 }}}
-------------------------
(1) {{{ 2 + x[B] = 10 }}}
(1) {{{ x[B] = 8 }}}
and
(2) {{{ -6 + y[B] = -2 }}}
(2) {{{ y[B] = 4 }}}
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The coordinates of B are: B( 8,4 )