Question 948651
They are shown in order of increasing x coordinate.  Check to see that the slopes between neighboring-listed points are all equal.  .....
.... They are equal.



That means, change in y divided by change in x is the same value between any pair of points listed.  Staying with purely algebraic thinking, what you do next depends on which form of equation you are comfortable to use.


{{{y=mx+b}}}; {{{m=-2/1}}}.


Choose ANY point from the list.
PICKING:  (4,9);
{{{mx+b=y}}}
{{{b=y-mx}}}
{{{b=9-(-2)(4)}}}
{{{b=9+8}}}
{{{b=17}}}
-
EQUATION:  {{{highlight(y=-2x+17)}}}