[tex]\text{First term,}~ a = 25\\\\\text{Common difference,} ~ d = 19-25 = -6\\\\\text{nth term} = a + (n-1)d\\\\~~~~~~~~~~~~~=25+(n-1)(-6)\\\\~~~~~~~~~~~~~=25-6n+6\\\\~~~~~~~~~~~~~=31-6n\\\\\text{4th term} = 31 - 6\times 4 = 7\\\\\text{5th term} = 31 - 6\times 5=1\\\\\text{6th term} =31-6*6 = -5\\\\\text{The series is}~ 25,19,13,\textbf{7,1,-5}...[/tex]
