Answer: y + 7
Step-by-step explanation:
If you use long division to divide y² - 49 by y - 7, you get the other factor y + 7
y + 7
____________
y - 7 ║ y² - 0 y - 49
- (y² - 7y) ↓
______________
+ 7y - 49
- (7y - 49)
___________
⇒ y² - 49 = (y - 7) (y + 7)
