I am beginning to study for my Calc 1 final by doing all of the old finals that are up on the math dept. page.

One question is:

If the line tangent to the graph of f (x) = x3 + 1 at the point (a, f (a)) passes

through the origin, then a is:

How am I to go about doing this? In all the practice I have done, and all the questions that have shown on my exam, a was given when it asked for a tangent line passing through a point (a,f(a)). So I don't know how to find a........