Let's try the one answer with no remainder: (b² - 3b + 18) If this is the answer, then, when multiplied by b+7, we should get b³+4b²-3b+126 (b+7) (b² - 3b + 18) Distribute = b³ - 3b² + 18b + 7b² - 21b + 126 Collect like terms = b³ + 4b²-3b + 126 This number perfectly matches the numerator in the first term!