Answer:
b < - 2 or b > 2
Step-by-step explanation:
Given
x² + 16 = 4bx ( subtract 4bx from both sides )
x² - 4bx + 16 = 0 ← in standard form
with a = 1, b = - 4b, c = 16
For the roots to be real the discriminant b² - 4ac > 0, that is
(- 4b)² - (4 × 1 × 16) > 0
16b² - 64 > 0
16(b² - 4) > 0 ← factor using difference of squares
16(b - 2)(b + 2) > 0, thus
b < - 2 or b > 2
