$x^{x}+x^{a}+a^{x}+a^{a}$, for some fixed $a>0$ and $x>0$
Let $y=x^{x}+x^{a}+a^{x}+a^{a}$
Also, let $x^{x}=u, x^{a}=v, a^{x}=w$, and $a^{a}=s$
$\therefore y=u+v+w+s$
$\Rightarrow \frac{d y}{d x}=\frac{d u}{d x}+\frac{d v}{d x}+\frac{d w}{d x}+\frac{d s}{d x}$ ...(1)
$u=x^{x}$
$\Rightarrow \log u=\log x^{x}$
$\Rightarrow \log u=x \log x$
Differentiating both sides with respect to x, we obtain'
$\frac{1}{u} \frac{d u}{d x}=\log x \cdot \frac{d}{d x}(x)+x \cdot \frac{d}{d x}(\log x)$
$\Rightarrow \frac{d u}{d x}=u\left[\log x \cdot 1+x \cdot \frac{1}{x}\right]$
$\Rightarrow \frac{d u}{d x}=x^{x}[\log x+1]=x^{x}(1+\log x)$ ...(2)
$v=x^{a}$
$\therefore \frac{d v}{d x}=\frac{d}{d x}\left(x^{a}\right)$
$\Rightarrow \frac{d v}{d x}=a x^{a-1}$ ...(3)
$w=a^{x}$
$\Rightarrow \log w=\log a^{x}$
$\Rightarrow \log w=x \log a$
Differentiating both sides with respect to x, we obtain
$\frac{1}{w} \cdot \frac{d w}{d x}=\log a \cdot \frac{d}{d x}(x)$
$\Rightarrow \frac{d w}{d x}=w \log a$
$\Rightarrow \frac{d w}{d x}=a^{x} \log a$ ...(4)
$s=a^{a}$
Since $a$ is constant, $a^{a}$ is also a constant.
Since a is constant, aa is also a constant.
$\therefore \frac{d s}{d x}=0$ ....(5)
From (1), (2), (3), (4), and (5), we obtain
$\frac{d y}{d x}=x^{x}(1+\log x)+a x^{a-1}+a^{x} \log a+0$
$=x^{x}(1+\log x)+a x^{a-1}+a^{x} \log a$