f(x)=x3sin3x+αsinx−βcos3x is continuous at x=0 x→0lim=x33x−∣3(3x)3+…+α(x−∣3x3…)−β(1−⌊2(3x)2…)=f(0) $\begin{aligned}
& \lim _{x \rightarrow 0}= \frac{-\beta+x(3+\alpha)+\frac{9 \beta x^2}{\underline{|2}}+\left(\frac{-27}{\underline{|3}}-\frac{\alpha}{\underline{|3}}\right) x^3 \ldots}{x^3}=f(0) \
& \text { for exist } \
& \beta=0,3+\alpha=0,-\frac{27}{\underline{|3}}-\frac{\alpha}{\underline{|3}}=f(0)
\end{aligned}\begin{aligned} & \alpha=-3,-\frac{27}{6}-\frac{(-3)}{6}=f(0) \ & f(0)=\frac{-27+3}{6}=-4\end{aligned}$