Skip to main contentSkip to solution

The function f(x)=x2+2x,x≠0f(x) = \frac{x}{2} + \frac{2}{x}, x \neq 0 is increasing on

(A) (−∞,−2)(-\infty, -2)

(B) (−2,2)(-2, 2)

(C) (2,∞)(2, \infty)

(D) (−1,1)(-1, 1)

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 3

A function is increasing where its derivative f′(x)>0f'(x) > 0.


Given: f(x)=x2+2xf(x) = \frac{x}{2} + \frac{2}{x}

Differentiating term by term:

Derivative of x2\frac{x}{2} is 12\frac{1}{2}

Derivative of 2x=2x−1\frac{2}{x} = 2x^{-1} is 2×(−1)×x−2=−2x22 \times (-1) \times x^{-2} = -\frac{2}{x^2}

Therefore:

f′(x)=12−2x2f'(x) = \frac{1}{2} - \frac{2}{x^2}


For the function to be increasing:

12−2x2>0\frac{1}{2} - \frac{2}{x^2} > 0

12>2x2\frac{1}{2} > \frac{2}{x^2}

x22>2\frac{x^2}{2} > 2

x2>4x^2 > 4

∣x∣>2|x| > 2

This means: x>2x > 2 or x<−2x < -2


Checking the options:

(A) (−∞,−2)(-\infty, -2) represents x<−2x < -2 — the function is increasing here

(B) (−2,2)(-2, 2) represents −2<x<2-2 < x < 2 — the function is not increasing here

(C) (2,∞)(2, \infty) represents x>2x > 2 — the function is increasing here

(D) (−1,1)(-1, 1) represents −1<x<1-1 < x < 1 — the function is not increasing here


The function is increasing on (−∞,−2)(-\infty, -2) and (2,∞)(2, \infty).

The correct answer is (A) and (C).

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question