Answer:
see explanation
Step-by-step explanation:
(b)
Given
x² - 8x + 20 = (x - 4)² + 4
(x - 4)² will be positive for all real values of x , except x = 4, where it will be zero.
Then (x - 4)² > 0, so
(x - 4)² + 4 > 0 , that is always positive
