To determine the factors of the expression xy + 3y + 7x + 21, we can group the terms in pairs:
- (xy + 3y) + (7x + 21)
Now, we can factor out the common terms from each pair:
- y(x + 3) + 7(x + 3)
Next, we can notice that both groups contain a common factor of (x + 3):
- (x + 3)(y + 7)
Thus, we can conclude that (x + 3) and (y + 7) are factors of the original expression xy + 3y + 7x + 21.