Consider the function f(x)=x2−4x+4+x2+6x+9f(x) = \sqrt{x^2 - 4x + 4} + \sqrt{x^2 + 6x + 9}f(x)=x2−4x+4+x2+6x+9. On which interval is f(x)f(x)f(x) constant?
x∈(−3,2)x \in (-3, 2)x∈(−3,2)
x∈[2,3]x \in [2, 3]x∈[2,3]
x∈[−3,2]x \in [-3, 2]x∈[−3,2]
x∈[0,5]x \in [0, 5]x∈[0,5]