Question 835033
If the any 2 of the slopes of the 
3 lines which are formed by the
3 points have the relationship:
{{{ m[2] = -1/m[1] }}}, then those
2 lines are perpendicular and
the triangle formed is a right triangle
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slope of ab:
a(3,4), b(3,1)
{{{ m[1] = ( 4-1 ) / ( 3-3 ) }}}
{{{ m[1] = 3/0 }}}
This is infinite slope, in other words,
a vertical line
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slope of bc:
b(3,1), c(2,5)
{{{ m[2] = ( 5-1 ) / ( 2-3 ) }}}
{{{ m[2] = 4/(-1) }}}
{{{ m[2] = -4 }}} 
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slope of ac:
a(3,4),c(2,5)
{{{ m[3] = ( 5-4 ) / ( 2-3 ) }}}
{{{ m[3] = 1/(-1)  }}}
{{{ m[3] = -1 }}}
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This looks like it's not a right triangle.
Check your data, but get a 2nd opinion, too