An inverse relation is one with the independent and dependent variables interchanged.
Having made that interchange (swapping positions of x and y in the equation), you basically cannot solve for y. (There is no formula for the solution of an 8th-degree polynomial.) In any event, this inverse relation is <em>not a function</em>, as there are multiple values of y that correspond to the same value of x.
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<em>Comment on inverse functions</em>
A function and its inverse are mirror images of each other across the line y=x. This can be seen in the attached graph.