\(\left(x-1\right)^2-\left(2x-2\right)\left(x+3\right)+\left(x+3\right)^2\)
=\(x^2-2x+1-2x^2+6x-2x-6+x^2+6x+9\)
=\(\left(x^2-2x^2+x^2\right)\)-\(\left(2x+2x-6x-6x\right)\)+\(\left(1-6+9\right)\)
=8x-4
=4(2x-1)
\(\left(x-1\right)^2-\left(2x-2\right)\left(x+3\right)+\left(x+3\right)^2\)
\(=\left(x-1\right)^2-2\left(x-1\right)\left(x+3\right)+\left(x+3\right)^2\)
\(=\left(x-1-x-3\right)^2\)
\(=\left(-4\right)^2=16\)