Finding Critical Points and Analyzing Function Behavior
Ever wonder how to find where a function peaks or dips? Critical points are where f'(x) = 0 or f'(x) is undefined—they're the key to finding important features on graphs! To determine where a function increases or decreases, analyze the sign of the first derivative.
When f'(x) > 0, the function is increasing. When f'(x) < 0, the function is decreasing. For example, to analyze y = -x⁴ - 4x³ + 20x² - 10, find f'(x) = -4x³ - 12x² + 40x, then locate where this equals zero: x = -5, 0, and 2. Testing points in each interval reveals where the function increases and decreases.
Concavity tells us about the shape of the graph. When f''(x) > 0, the function is concave up (smiles), and when f''(x) < 0, it's concave down (frowns). A point of inflection occurs where concavity changes—this happens when f''(x) = 0 and changes sign.
Remember: When analyzing functions, create a number line with your critical points and test the sign of f'(x) in each interval—this visual approach helps avoid confusion!
For trigonometric functions like f(x) = 12 + 4x - 3tan x, the same principles apply, but you'll need to work with the appropriate domain restrictions like(0,π/2) and use trigonometric identities to solve.