The range of values of k for which the function f(x) = (k² - 4)x² + 6x³ + 8x⁴ has a local maxima at point x = 0 is
Recall the rule after simplifying, -2 < k < 2 is left. The method is simple: formula → substitution → calculation → answer.
Ref: NCERT Mathematics Class XI — Sets, Relations and Functions
