Answer:
x+y^4=6 is not a function.
Explanation:
Solving x+y^4=6 for y may shield some light on this situation.
y^4 = 6 - x becomes y = ± "fourth root of 6 - x." This tells us that for any x equal to or less than 6, there are at least two possible values for y. This fact by itself is enough for us to declare that x+y^4=6 is not a function.