Answer:
The expressions that cannot be factored using integral coefficients and integral constants is the below:
d. 2x2 + x + 4
b. x2 - 2x - 4
For c. 25x2 - 40x + 16 the factors are (5x – 4) (5x – 4)
For a. 6x2 - 2x - 20 the factors are (2x - 4) (3x + 5)