$If\ the\ r\ th\ term\ in\ the\ expansion\ of\ \left( \frac{x}{3} - \frac{2}{x^{2}} \right)^{10}\ contains\ x^{4},then\ r\ is\ equal\ to$

Question

Dr. Abubacker · Accepted Answer

(a)
$	herefore T_{r} = 10_{C_{r - 1}}\left( \frac{x}{3} ight)^{11 - r}\left( \frac{- 2}{x^{2}} ight)^{r - 1}$
$\ \ \ \ \ \ \ \ \  = 10_{C_{r - 1}}(x)^{13 - 3r}(3)^{- 11 + r}( - 1)^{r - 1}(2)^{r - 1}$
For $x^{4},$ we put $13 - 3r = 4 \Longrightarrow r = 3$

Q. $If\ the\ r\ th\ term\ in\ the\ expansion\ of\ \left( \frac{x}{3} - \frac{2}{x^{2}} \right)^{10}\ contains\ x^{4},then\ r\ is\ equal\ to$

Explanation

Reviewed by Dr. Abubacker

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