So...
Y=3x/(x^2+9), plug in 0 for Y.
0=3x/(x^2+9), multiply both sides by denominator
0=3x, at y=, x=0. Intercept at origin (:
For
Y=(3x/x^2)+9, plug in 0 for Y
0= (3x/x^2)+9,subtract both sides
-9=(3x/x^2), divide by x on the right
-9=3/x, multiply by x to the other side
-9x=3, and divide by -9
X=-1/3 or -.33333. At x =0 is null, because it's division by 0 (: so no y Intercept