Answer:
In general, y = ax³ + bx² + cx + d
Where a,b,c & d are real,
Y can have at max 3 real roots, or one real and a conjugate pair of complex roots.
Also, -d/a is the product of roots
13) positive real values: 0 or 2
negative real values: 1 or 3
Imaginary roots: 0 or 2
14) positive real values: 1 or 3
negative real values: 0 or 2
Imaginary roots: 0 or 2