Therefore, from the given equation,
\(x^{2}-16 x+39=0\)
\(\Rightarrow x^{2}-13 x-3 x+39=0\)
\(\Rightarrow x(x-13)-3(x-13)=(x-13) \times(x-3)=0\)
\(\Rightarrow x=13\) or \(3\)
\(\therefore m=3\) and \(n=13\)
Now, it is given that, four terms \(p, q, r\) and \(s\) are inserted between \(m\) and \(n\) to form an AP.
We know that for an AP, if the first term is \(a\) and common difference is \(d\), then,
Second term = \(a+d\)
Third term = \(a+2d\) & so on.
Therefore, according to the question,
\( p+q+r+s=(m+d)+(m+2 d)+(m+3 d)+(m+4 d)\)
\(\Rightarrow p+q+r+s=4 m+10 d\)
\(\Rightarrow p+q+r+s=2 \times(2 m+5 d)\)
\(\Rightarrow p+q+r+s=2 \times[m+(m+5 d)]\)
\(\Rightarrow p+q+r+s=2 \times(m+n) \quad [\because(n=m+5 d)]\)
\(\Rightarrow p+q+r+s=32\quad [\because(m+n=16)]\)