Let $\displaystyle (a, c)$ and $\displaystyle (b, d)$ be the roots of the equation $\displaystyle x^2 + ax - b = 0$ and $\displaystyle x^2 + cx + d = 0$ respectively. Find all possible real values for $\displaystyle a, b, c, d$

I'm not sure how to do this question and not sure how to approach it.

Please help, BG