To simplify the expressions and arrange the terms by their degree, we can write:
$\longrightarrow\sf\textbf\:f(x)\:= -x^4\:+\:2x^2\:-\:5x\:+\:3$
$\longrightarrow\sf\textbf\:=\:-x^4 + 2x^2 - x - 4x + 3$
$\longrightarrow\sf\textbf\:=\:-x(x^3 - 2x + 1) - 4x + 3$
$\longrightarrow\sf\textbf\:g(x)\:=\:x^4 + 4x^2 + 2x + 1$
$\longrightarrow\sf\textbf\:x^4 + 4x^2 + 2x + 1 - 2 + 2$
$\longrightarrow\sf\textbf\:x^4 + 4x^2 + 2x - 1 + 2$
$\longrightarrow\sf\textbf\:x^4 + 4x^2 + 2x - 1 + 2$
$\longrightarrow\sf\textbf\:x^4 + 4x^2 + 2x + 1 - 2$
$\longrightarrow\sf\textbf\:(x^2 + 1)^2 - 2$
Therefore, we can express the simplified forms of ${\sf{\textbf{f(x)}}}$ and ${\sf{\textbf{g(x)}}}$ as:
$\longrightarrow\sf\textbf\:f(x)\:=\:-x(x^3 - 2x + 1) - 4x + 3$
$\longrightarrow\sf\textbf\:g(x)\:=\:(x^2 + 1)^2 - 2$



