\(x^2+3cd\left(2-3cd\right)-10xy-1+25y^2\)
\(=\left[x^2-2x5y+\left(5y\right)^2\right]-\left[1-6cd+9\left(cd\right)^2\right]\)
\(=\left(x-5\right)^2-\left[\left(3cd\right)^2-2.3cd+1^2\right]\)
\(=\left(x-5\right)^2-\left(3cd-1\right)^2\)
\(=\left(x-5+3cd-1\right)\left(x-5-3cd+1\right)\)