Question 1086814
<pre><b>

There are two possible coordinates of B.
Here are the graphs for each:

{{{drawing(35400/99,600,-1.9,9.9,-9.9,9.9,

graph(35400/99,600,-1.9,9.9,-9.9,9.9),
locate(.5,.6,"A(2,0)"), locate(8.4,8.4,"B(8,?)"),
locate(8.1,4,"y=?"),
red(line(2,0,8,8)), locate(4,4,10),
green(line(8,0,8,8))
 )}}}  {{{drawing(35400/99,600,-1.9,9.9,-9.9,9.9,

graph(35400/99,600,-1.9,9.9,-9.9,9.9),
locate(.5,.6,"A(2,0)"), locate(8.4,-8.4,"B(8,?)"),
locate(8.1,-4,"y=?"),
red(line(2,0,8,-8)), locate(4,-4,10),
green(line(8,0,8,-8))
 )}}}

Count the units on the horizontal side of the right
triangle.  The hypotenuse is given to be 10.  Then
use the Pythagorean theorem to calculate the value
of y.  It will be positive for the first possibility
and negative for the second.

You finish.

Edwin</pre>