Why do math problems have two answers?

Answer 1

Assuming that you are reffering to something like this:

(x - h)(x - k) = 0

x = h, x = k

This is the fundamental theorem of algebra which states that is given a polynomial (multiple terms raised to positive powers ex) x^3 + 2x + 1), then the number of solutions to that polynomial is equal to the degree (or highest exponent) in the polynomial. The factorization in the beginning was dealing with a quadratic equation - when foiled out it equals x^2 - hx - kx + hk. The highest exponent in the quadratic is two and therefore there are two solutions. You can even think back to the factorization again: if x = h then the whole equation is 0, if x = k then the whole equation is 0.