Question 129779
Well, if you are sure about that second point, you can use the two-point form of the line:


{{{y-y[1]=((y[1]-y[2])/(x[1]-x[2]))(x-x[1])}}}


Lets say that {{{P[1]}}} is (0,3) and {{{P[2]}}} is (-3,0).  (It doesn't matter which point you call 1 and which you call 2 as long as you keep it consistent.)  That means that:


{{{x[1]=0}}},
{{{y[1]=3}}},
{{{x[2]=-3}}}, and
{{{y[2]=0}}}.


Just plug in the numbers and do the arithmetic:
{{{y-3=((3-0)/(0-(-3)))(x-0)}}}


{{{y-3=(3/3)(x)}}}


{{{y-3=x}}}


{{{y=x+3}}}




If the graph you are working with looks like this, then we have it pretty close anyway.



{{{drawing(400,400,-5,5,-5,5,
grid(1),
graph(400,400,-5,5,-5,5,x+3)
)}}}