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x² + 2xy + y² - 2x - 2y – 15 = 0(x + y)² - 2(x+ y) – 15 = 0(x + y – 5)(x + y + 3) = 0 x + y – 5 = 0 or x + y + 3 = 0 Since there’s no solution for these 2 equations, so x² + 2xy + y² - 2x - 2y – 15 = 0 represent 2 // lines.