Is there an equation that gives the horizontal distance travelled of an object projected at an angle (theta) with an initial velocity (V0) and given that the object lands (y) above/below where it was launched?
Of course. Just use the same equations you would if the landing point were on the same level:
x= v0cos(θ)t, y= v0sin(θ)t- (g/2)t2.
Let y0 be the height of the landing point relative to the starting point (0 is same level, negative if below, positive if above). Solve
y= v0sin(θ)t- (g/2)t2= y0 for t. (You will get two solutions the time for the landing is the larger of the two).
Since that is a quadratic equation, use the quadratic formula:
Now put that value of t in the equation for x (use the positive sign for the root to get the larger of the two solutions):
A bit more complicated than the case y0= 0 but still a valid formula. Notice that when y0= 0 that reduces to
the usual formula.
I would consider it easier to solve the equations than to memorize that formula.