The answer to this question is both 4 and -7/2 factor and then set both parenthesise equal to zero and solve

2x^2 - x - 28 < 0

(2x +7) (x-4) = 0

x = -7/2 or x = 4

but this is an inequality so

check in the function

you get

-7/2

(2x +7) (x-4) = 0

x = -7/2 or x = 4

but this is an inequality so

check in the function

you get

-7/2