a) ta có : \(x^3-64=x^3-4^3=\left(x-4\right)\left(x^2+4x+16\right)\)
b) ta có : \(125x^3+y^6=\left(5x\right)^3+\left(y^2\right)^3=\left(5x+y^2\right)\left(25x^2-5xy^2+y^4\right)\)
c) ta có : \(125\left(x+1\right)^3-1=\left(5x+5\right)^3-1\)
\(=\left(5x+5-1\right)\left(\left(5x+5\right)^2+\left(5x+5\right)+1\right)\)
\(=\left(5x+4\right)\left(25x^2+55x+31\right)\)
d) ta có : \(2x\left(x+1\right)+2\left(x+1\right)=\left(2x+2\right)\left(x+1\right)=2\left(x+1\right)\left(x+1\right)\)