Final answer:
To find the interval on which f(x) is increasing, we need to determine where the derivative of f(x) is positive. The interval on which f(x) is increasing is (-∞, -3) U (3, ∞).
Step-by-step explanation:
To find the interval on which f(x) is increasing, we need to determine where the derivative of f(x) is positive. The derivative of f(x) is found by using the quotient rule:
f'(x) = (1*(x^2 + 9) - x*(2x))/(x^2 + 9)^2
Simplifying this expression gives:
f'(x) = (9 - x^2)/(x^2 + 9)^2
To find where f'(x) is positive, we need to solve the inequality:
(9 - x^2)/(x^2 + 9)^2 > 0
Using a sign chart, we can determine that f'(x) is positive for x < -3 and x > 3. Therefore, the interval on which f(x) is increasing is (-∞, -3) U (3, ∞).