#### Answer

$2x+1$; $x^2-14x+49$

#### Work Step by Step

Square both sides of the equation to obtain:
$\sqrt{2x+1}^2 = (x-7)^2
\\2x+1 = (x-7)^2$
Use the formula $(a-b)^2 = a^2-2ab+b^2$ where $a =x$ and $b=7$ to obtain:
$2x+1=x^2-2(x)(7) + 7^2
\\2x+1 = x^2 - 14x + 49$
Thus, the missing expressions in the given statements are $2x+1$ and $x^2-14x+49$, respectively.