Find an recursive formula for the geometric sequence $\displaystyle {H}_{{n}}={\left\lbrace-{20},{15},-{11.25},{8.4375},\ldots\right\rbrace}$

$\displaystyle {H}_{{1}}=$
$\displaystyle {H}_{{n}}={H}_{{{n}-{1}}}\ast$Preview Question 6 Part 2 of 2