Answer:
D : [tex]x^{2} +81=x^{2} +20x+100[/tex]
Step-by-step explanation:
We start with the original equation:
[tex]\sqrt{x^{2} +81} =x+10[/tex]
Squaring both sides to remove the square root we get:
[tex]x^{2} +81=(x+10)^{2}[/tex]
Expanding the right side:
[tex]x^{2} +81=(x+10)(x+10)[/tex]
Multiplying the right side out and combining like terms we get:
[tex]x^{2} +81=x^{2} +20x+100[/tex]
