Question 962123
The format for points is:
( x, y ), so given ( k, k+1 ), I have:
{{{ x = k }}}
{{{ y = k + 1 }}}
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{{{ y = 3x - 1 }}}
{{{ k+1 = 3k - 1 }}}
{{{ 2k = 2 }}}
{{{ k = 1 }}}
and
{{{ k + 1 = 1 + 1 }}}
{{{ k + 1 = 2 }}}
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When {{{ k = 1 }}}, the point 
( k, k+1 ) is on the line
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check:
{{{ y = 3x - 1 }}}
{{{ 2 = 3*1 - 1 }}}
{{{ 2 = 3 - 1 }}}
{{{ 2 = 2 }}}
OK