Respuesta :

try grouping in paires

4x^3 + 28x^2 + 7x + 49

= 4x^2(x + 7) + 7(x + 7)  - note  that (x + 7) is common to the 2 parts, so

=  (4x^2 + 7)(x + 7)
(x+7) (4x²+7) is the correct answer