a, \(16x^7+5x^4=x^4\left(16x^3+5\right)\)
b, \(x^2yz+x^2y^2z^2+x^2yz^2=x^2yz\left(1+yz+yz^2\right)\)
c, \(5x^n+10x^{n+2}=5x^n+10x^n.x^2\)
\(=5x^n\left(1+2x^2\right)\)
d, \(\left(x+y\right)^3-x^3-y^3\)
\(=x^3+2x^2y+2xy^2+y^3-x^3-y^3\)
\(=2x^2y+2xy^2=2xy\left(x+y\right)\)