Solution:Given, n is a root of x² + px + m = 0⇒ n² + pn + m = 0 ....(i)
Given, m is a root of the equation x² + px + n = 0 ⇒ m²+ pm + n = 0 ...(ii)
Now subtracting Eq (ii) from Eq (i), we get
(n² - m²) + p(n - m) - (n - m) = 0
⇒ (n - m) [(n + m) + p - 1] = 0
⇒ n + m + p - 1 = 0 {given, n ≠ m }
⇒ n + m + p = 1