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Which of the following statements are correct ?

A. The function f(x)=axf(x) = a^x is increasing on (−∞,∞)(-\infty,\infty) if a>1a>1.

B. f(x)=x2−2xf(x) = x^2 - 2x is decreasing in (−∞,1)(-\infty,1).

C. f(x)=x(x−3)2f(x) = x(x-3)^2 increases for 1≤x≤31 \le x \le 3.

D. f(x)=e−xf(x) = e^{-x} decreases in [0,∞)[0,\infty).

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 2

A: ddxax=axlog⁡a>0\dfrac{d}{dx}a^x=a^x\log a>0 for a>1a>1, increasing. True.

B: f′=2x−2<0f'=2x-2<0 for x<1x<1, decreasing. True.

C: f′=3(x−1)(x−3)<0f'=3(x-1)(x-3)<0 on (1,3)(1,3), so it decreases there. False.

D: f′=−e−x<0f'=-e^{-x}<0, decreasing. True.

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