Faktorkanlah 9x^2 - 81x^2y^2 - x^2 + 9y^2 (perhatikan

Faktorkanlah 9x^2 - 81x^2y^2 - x^2 + 9y^2 (perhatikan contoh)! Contoh: a^2b^2 - a^2c - b^2 + c^2 = (a^2b^2 - a^2c^2) - (b^2 - c^2) = a^2(b^2 - c^2) - 1(b^2 - c^2) = (b^2 - c^2)(a^2 - 1) = (b + c)(b -c)(a + 1)(a - 1)