25(x-2y)的平方-4(2y-x)的平方
=【5(x-2y)】^2-【2(2y-x)】^2
=[5(x-2y)-2(2y-x)]*[5(x-2y)+2(2y-x)]
=(7x-14y)*(3x-6y)
=21(x-2y)*(x-2y)
=21(x-2y)^2
25(x-2y)的平方-4(2y-x)的平方
=【5(x-2y)】^2-【2(2y-x)】^2
=[5(x-2y)-2(2y-x)]*[5(x-2y)+2(2y-x)]
=(7x-14y)*(3x-6y)
=21(x-2y)*(x-2y)
=21(x-2y)^2