a: =2xy*x-2xy*2y+2xy*3
=2xy(x-2y+3)
b: =2x^2y*2xy-2x^2y*4y^2+2x^2y*x^2
=2x^2y(2xy-4y^2+x^2)
c: \(=3xy^2\cdot3xy-3xy^2\cdot x^3-3xy^2\cdot2x^2+3xy^2\cdot6y^2\)
\(=3xy^2\left(3xy-x^3-2x^2+6y^2\right)\)
d: \(=7xy\cdot xy-7xy\cdot3yz+7xy\cdot z-7xy\cdot2\)
\(=7xy\left(xy-3yz+z-2\right)\)