Question

Which shows one way to determine the factors of x3 + 4x2 + 5x + 20 by grouping?

Answer 1

x3+4x2+5x+20
x2(x+4)+5(x+4)
(x2+5) (x+4)

Answer 2

It is best way to ensure factors of x 3 + 4 x 2 + 5x + 20 which given, we can group it as x3 + 4 x 2 + 5x + 20,

we have to factor out the common factor as  x2 (x+4) + 5 (x+4) = (x2+5) (x+4).  

So, the answer of grouping the factors is (x2+5) (x+4).