1.（x-2y)^2+ 14(2y-x)+49
=（x-2y)^2-2*7*(x-2y)+49
=(x-2y-7)^2
2.(x+2y)^3- (x+2y)
=(x+2y)[(x+2y)^2-1]
=(x+2y)(x+2y+1)(x+2y-1)