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)
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)