a, \(x\left(x+4\right)\left(x+6\right)\left(x+16\right)+128\)
\(=\left(x^2+4\text{x}\right)\left(x+6\right)\left(x+16\right)+128\)
\(=\left(x^3+10x^2+24x\right)\left(x+16\right)+128\)
\(=x^4+26x^3+184x^2+384x+128\)
b, \(x^3-4\text{x}^2-12\text{x}+24\)(Đề sai chăng??)
c, \(x^2-4+\left(x-2\right)^2\)
\(=\left(x-2\right)\left(x+2\right)+\left(x-2\right)^2\)
\(=\left(x-2\right)\text{[}\left(x+2\right)+\left(x-2\right)\)
\(=\left(x-2\right)\left(x+2+x-2\right)\)
\(=\left(x-2\right)2\text{x}\)