so basycilly slope intercept form is y=mx+b where m=slope and b=y intercept
slope=-1
subsiute
y=-1x+b
y=-x+b
so we are given the point (-3,2)
x=-3 and y=2 is one solution
subsitue and solve for b
2=-(-3)+b
2=3+b
subtract 3 from both sides
-1=b
the slopt inercetp form is y=-x-1