# test diff

$\\displaystyle \\left(\\frac{d}{d x} g{\\left(x \\right)} + 1\\right) \\left. \\frac{d}{d \\xi\_{1}} f{\\left(\\xi\_{1} \\right)} \\right|*{\\substack{ \\xi*{1}=x + g{\\left(x \\right)} }}$