Answer:
[tex]x^{2}[/tex] + 40x + 400
Step-by-step explanation:
[tex](x + 20)^{2}[/tex]
(x + 20)(x + 20)
(x)(x) + (x)(20) + (20)(x) + (20)(20)
[tex]x^{2}[/tex] + 20x + 20x + 400
