Hi, I have an 'advanced quadratic' problem which I'm not sure how to solve.

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

Thanks for any help, BG