If $|x| \lt \frac{2}{2}$ then the $4^{\text {th }}$ term in the expansion of $(3 x-2)^{2 / 3}$ is
If $|x| \lt \frac{2}{2}$ then the $4^{\text {th }}$ term in the expansion of $(3 x-2)^{2 / 3}$ is
- $\frac{\sqrt[3]{4}}{6} x^3$
- $-\frac{\sqrt[3]{4}}{6} x^3$
- $\frac{\sqrt[3]{4}}{8} x^3$
- $-\frac{\sqrt[3]{4}}{8} x^3$
Solution
$(3 x-2)^{\frac{2}{3}}=\left[-2\left(1-\frac{3 x}{2}\right)\right]^{\frac{2}{3}}=(-2)^{\frac{2}{3}}\left(1-\frac{3 x}{2}\right)^{\frac{2}{3}}$
$\begin{aligned} & =\sqrt[3]{4}\left(1-\frac{3 x}{2}\right)^{\frac{2}{3}} \\ & T_4=-\sqrt[3]{4} \frac{\frac{2}{3}\left(\frac{2}{3}-1\right)\left(\frac{2}{3}-2\right)}{3!}\left(\frac{3 x}{2}\right)^3 \\ & =-\sqrt[3]{4} \times \frac{1}{6} \times \frac{2}{3} \times\left(\frac{-1}{3}\right)\left(\frac{-4}{3}\right) \times \frac{27}{8} x^3=-\frac{\sqrt[3]{4}}{6} x^3\end{aligned}$
Asked in: AP EAMCET 2024 (20 May Shift 2)
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