Polynomial: Find x given y

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I've been given a cubic polynomial, with values a, b, c, and d, and have been asked to find the point x given a y value.

I can factor the function easily enough, but I do not know how to isolate x algebraically given y.

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So it sounds like you are trying to solve $$p(x) = C$$ where $p(x)$ is a cubic function, and $C$ is a given constant.

You say that you know how to factor $p(x)$. That's good -- but it's actually not particularly helpful in this case, as it doesn't help you get to a solution.

Instead, rewrite the equation as $$p(x) - C = 0$$ and see if you can factor the new polynomial that appears on the left-hand side. If you can factor it, you can easily find the zeroes of $p(x)-C$, which are then the solutions of your equation.