Question 914271
By looking at it, I see:
{{{ x^2  - 6x*y + 9y^2 = 25 }}}
{{{ ( x - 3y )^2 = 5^2 }}}
Take the square root of both sides
{{{ x - 3y = 5 }}}
and
{{{ x - 3y = -5 }}}
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{{{ 3y = x - 5 }}}
(1) {{{ y = (1/3)*x - 5/3 }}}
and also:
{{{ 3y = x + 5 }}}
(2) {{{ y = (1/3)*x + 5/3 }}}
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{{{ graph( 400, 400, -10, 10, -10, 10, (1/3)*x  - 5/3, (1/3)*x + 5/3 ) }}}