Write the $r^{t h}$ term from the end in the expansion of $(x + a)^{n}$

^{n} C_{n - r + 1} (x)^{r - 1} (a)^{n - r + 1}

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^{n} C_{n - r + 1} (x)^{r} (a)^{n - r + 1}

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^{n} C_{n - r} (x)^{r} (a)^{n - r}

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^{n} C_{n - r} (x)^{r - 2} (a)^{n - r}

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Solution

The correct option is C $^{n} C_{n - r} (x)^{r} (a)^{n - r}$
$r^{t h} t e r m f r o m t h e e n d m e a n s = (n - r + 1)^{t h} t e r m f r o m t h e b e g i n i n g ∴ T_{n - r + 1} =^{n} C_{n - r} x^{r} a^{n - r}$

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Similar questions

^{n} C_{n - r} + 3^{n} C_{n - r + 1} + 3.^{n} C_{n - r + 2} +^{n} C_{n - r + 3} =^{x} C_{r}

x = n + k

k

^{n} C_{n - r} + 3^{n} C_{n - r + 1} + 3^{n} C_{n - r + 2} +^{n} C_{n - r + 3} =^{p} C_{r}

p = n + 3

here r/nCr=(n-r)/nCn-r how it is possble because its true that nCr=nCn-r but how n-r=r as in numerator

^{n} C_{n - r}

^{n} C_{r} =^{n} C_{n - r}

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