\(a,3x^2-4y+4x-3y^2\)
\(=3x^2-3y^2+4x-4y\)
\(=3\left(x^2-y^2\right)+4\left(x-y\right)\)
\(=3\left(x-y\right)\left(x+y\right)+4\left(x-y\right)\)
\(=\left(x-y\right)\left(3x+3y+4\right)\)
\(b,2x^2-6xy+5x-15y\)
\(=2x\left(x-3y\right)+5\left(x-3y\right)\)
\(=\left(2x+5\right)\left(x-3y\right)\)
\(c,10ax-5ay-2x+y\)
\(=5a\left(2x-y\right)-\left(2x-y\right)\)
\(=\left(5a-1\right)\left(2x-y\right)\)