Hi. Using polynomial regression, determine a third degree polynomial that decreases that follows these digits

Let x=0 be 1990

Year Total Forest 2003 31.1 Area (% of Land Area) 2004 1990 31.6 31 1991 31.6 2005 31 1992 31.6 2006 31 1993 31.6 2007 30.9 1994 31.5 2008 30.9 1995 31.5 2009 30.9 1996 31.4 2010 30.9 1997 31.3 2011 30.8 1998 31.3 201 30.8 1999 31.2 2013 30.8 2000 2014 31.2 30.8 2001 31.1 2015 30.7 2002 31.1 2016 30.7