\(\left(3x-1\right)^4+2\left(9x^2-6x+1\right)+1\)
\(=\left[\left(3x-1\right)^2+1\right]^2\)
\(=\left(9x^2-6x+2\right)^2\)
\(=\left(3x-1\right)^4+2\left(3x-1\right)^2+1\\ =\left[\left(3x-1\right)^2+1\right]^2\\ =\left(9x^2-6x+2\right)^2\)
c) Ta có:
\(\left(3x-1\right)^4+2\left(9x^2-6x+1\right)+1=\left[\left(3x-1\right)^2\right]^2+2\left(3x-1\right)^2.1+1^2=\left[\left(3x-1\right)^2+1\right]^2\)