7y-2
=2x+y-2x+6y
=(2x+y)-2(x-3y)
=6-2
=4

7y(x-3y)(x-3y)-2(3y-x)(3y-x)
=7y(x-3y)(x-3y)-2(x-3y)(x-3y)x-3y=1
=7y-2 7y-2=4
=4