(x + 3*y)*(x - 3*y)
(x + 3*y)*(x - 3*y) при y = -2
(x + 3*(-2))*(x - 3*(-2))
(-6 + x)*(6 + x)
(x - 3*y)*(x + 3*y)
(x + 3.0*y)*(x - 3.0*y)
2 2 x - 9*y