Three polynomials are factored below, but some coefficients and constants are missing. All of the missing values of a, b, c, and d are integers.
1. x² + 2x - 15 = (ax + b)(cx + d)
2. 2x³ + 6x^2 - 20x = 2x(ax + b)(cx + d)
3.9x² +21x + 6 = (ax + b)(cx + d)
Fill in the table with the missing values of a, b, c, and d.
A B C D
1. 1 -3 1. _
2. 1 _ _ 5
3. _ 6 3 _