Answer:
[tex] {x}^{2} + 10x + 21[/tex]
Step-by-step explanation:
[tex](x + 7)(x + 3) \\ = x(x + 3) + 7(x + 3) \\ = {x}^{2} + 3x + 7x + 21 \\ \purple{ \bold{= {x}^{2} + 10x + 21}}[/tex]
