The function $f(x) = x + \frac{1}{x}$ has |
local maxima at $x = -1$ local minima at $x = -1$ local maxima at $x = 1$ neither local maxima nor local minima |
local maxima at $x = -1$ |
The correct answer is Option (1) → local maxima at $x = -1$ Given $f(x) = x + \frac{1}{x}$. Differentiate: $f'(x) = 1 - \frac{1}{x^2}$ Setting $f'(x) = 0$: $1 - \frac{1}{x^2} = 0$ $x^2 = 1$ $x = \pm 1$ Second derivative: $f''(x) = \frac{2}{x^3}$ At $x = 1$: $f''(1) = \frac{2}{1^3} = 2 > 0$ (local minimum). At $x = -1$: $f''(-1) = \frac{2}{(-1)^3} = -2 < 0$ (local maximum). Local maxima occur at $x = -1$ with value: $f(-1) = -1 + \frac{1}{-1} = -1 - 1 = -2$. |