x = -16 or x = 5
Solution:
Given polynomial:

To find the roots of the polynomial.
Split the middle term 11x.
11x = 16x - 5x



Take the x common in first 2 terms an -5 common in next 2 terms.

Take (x + 16) common in both terms.

x + 16 = 0 or x - 5 = 0
x = -16 or x = 5
Hence x = -16 or x = 5.