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JEE Main 20245 AprilMorning Shift
Exam
JEE Main
Year
2024
Date
5 April
Shift
Morning Shift
Subject
Mathematics
Chapter
Continuity and Differentiability

JEE Main 2024 · 5 April · Morning Shift · Mathematics · Continuity and Differentiability

If the function f(x)=( 3 x+α x-β 3 x)/(x^3), x ∈ R , is continuous...

If the function f(x)=sin⁡3x+αsin⁡x−βcos⁡3xx3,x∈Rf(x)=\frac{\sin 3 x+\alpha \sin x-\beta \cos 3 x}{x^3}, x \in \mathbf{R}, is continuous at x=0x=0, then f(0)f(0) is equal to :

Options

  1. A2
  2. B-2
  3. C4
  4. D-4

Correct answer

D. -4

Step-by-step solution

f(x)=sin⁡3x+αsin⁡x−βcos⁡3xx3f(x)=\frac{\sin 3 x+\alpha \sin x-\beta \cos 3 x}{x^3} is continuous at x=0lim⁡x→0=3x−(3x)3∣3‾+…+α(x−x3∣3‾…)−β(1−(3x)2⌊2…)x3=f(0)\mathrm{x}=0 \lim _{x \rightarrow 0}=\frac{3 x-\frac{(3 x)^3}{\underline{|3}}+\ldots+\alpha\left(x-\frac{x^3}{\underline{|3}} \ldots\right)-\beta\left(1-\frac{(3 x)^2}{\lfloor 2} \ldots\right)}{x^3}=f(0)lim⁡x→0=−β+x(3+α)+9βx2∣2‾+(−27∣3‾−α∣3‾)x3…x3=f(0) for  exist β=0,3+α=0,−27∣3‾−α∣3‾=f(0)\begin{aligned} & \lim _{x \rightarrow 0}= \frac{-\beta+x(3+\alpha)+\frac{9 \beta x^2}{\underline{|2}}+\left(\frac{-27}{\underline{|^{3}}}-\frac{\alpha}{\underline{|^{3}}}\right) x^3 \ldots}{x^3}=f(0) \\ & \text{\text{ for } exist } \\ & \beta=0,3+\alpha=0,-\frac{27}{\underline{|3}}-\frac{\alpha}{\underline{|^{3}}}=f(0) \end{aligned}α=−3,−276−(−3)6=f(0)f(0)=−27+36=−4\begin{aligned} & \alpha=-3,-\frac{27}{6}-\frac{(-3)}{6}=f(0) \\ & f(0)=\frac{-27+3}{6}=-4\end{aligned}$$
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