Question

Help me find the answer for this problem, please.

Answer 1

$f(x+a)-f(x)=\sqrt{x+a+7}+7-(\sqrt {x+7}+7})\\ f(x+a)-f(x)=\sqrt{x+a+7}+7-\sqrt {x+7}-7}\\ f(x+a)-f(x)=\sqrt{x+a+7}-\sqrt {x+7}$