\(4)\left(3x+y\right)^2+\left(x-y\right)^2\\ =9x^2+6xy+y^2+x^2-2xy+y^2\\ =10x^2+4xy+2y^2\\ 5)-\left(x+5\right)^2-\left(x-3\right)^2\\ =-\left(x^2+10x+25\right)-\left(x^2-6x+9\right)\\ =-x^2-10x-25-x^2+6x-9\\ =-2x^2-4x-34 \\ 6)\left(3x-2\right)^2-\left(3x-1\right)^2\\ =\left(9x^2-12x+4\right)-\left(9x^2-6x+1\right)\\ =9x^2-12x+4-9x^2+6x-1\\ =-6x+3\)
4: \(\left(3x+y\right)^2+\left(x-y\right)^2\)
\(=9x^2+6xy+y^2+x^2-2xy+y^2\)
\(=10x^2+4xy+2y^2\)
5: \(-\left(x+5\right)^2-\left(x-3\right)^2\)
\(=-x^2-10x-25-x^2+6x-9\)
\(=-2x^2-4x-34\)
6: \(\left(3x-2\right)^2-\left(3x-1\right)^2\)
\(=\left(3x-2-3x+1\right)\left(3x-2+3x-1\right)\)
\(=-1\left(6x-3\right)=-6x+3\)
