Question

(3x+1)^4

Answer 1

expanded form: 81 x^4+108 x^3+54 x^2+12 x+1
root: x= -1/3

Answer 2

x^4 + (4-choose-1)x^3*1^3 and go on...

Answer 3

\[(a+b)^4=a^4+4a^3b+10a^2b^2+4ab^3+b^4\]
use
\[a=3x,b=1\]

Answer 4

use binomial theorem for expansion