When factoring x^2 + bx + c and c is positive, what must be true about the signs of m and n in (x+m)(x+n)?

1. The rule for factoring trinomials states that when c is positive, m and n share the same sign. 2. If b is also positive, both m and n are positive, as in x squared + 5x + 6 factoring to (x + 2)(x + 3). 3. If b is negative, both m and n are negative instead, as in x squared - 6x + 8 factoring to (x - 4)(x - 2). 4. Opposite signs for m and n only happen when c itself is negative, which is a different case. _Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 7 "Factoring", section 7.2 Factor Quadratic Trinomials with Leading Coefficient 1_