Answer:
The range is y ≥ -1
Explanation:
∵ f(x) = (x - 4)(x - 2)
∴ f(x) = x² - 2x - 4x + 8
∴ f(x) = x² - 6x + 8 ⇒ quadratic function (ax² + bx + c) represented by
parabola graphically
∵ a = 1 , b = -6 , c = 8
∴ x-coordinate of its vertex = -b/2a = -(-6)/2×1 = 3
∴ f(3) = (3)² - 6(3) + 8 = -1
∵ a is positive ⇒ the curve has minimum point and it's open upward
∴ the minimum point is (3 , -1)
∴ The range is y ≥ -1 ⇒ because the minimum value is -1