When factoring x^2 + bx + c and c is negative, 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 negative, m and n take opposite signs. 2. A negative product like c requires one positive and one negative factor. 3. The sign of whichever factor has the larger absolute value matches the sign of b, which decides which factor is positive and which is negative. 4. Same-sign factors for m and n only happen when c itself is positive, 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_