The ratio of (r+1)th and rth terms in the expansion of $(1 - x)^{n}$ is

\frac{- r}{(n - r + 1) x}

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\frac{r}{(n - r + 1) x}

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\frac{- (n - r + 1) x}{r}

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\frac{(n - r + 1) x}{r}

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Solution

The correct option is B $\frac{- (n - r + 1) x}{r}$
$T_{r}$ th term
$= (- 1)^{r - 1}^{n} C_{r - 1} x^{r - 1}$ ...(i)
And $T_{r + 1}$ th term
$= (- 1)^{r}^{n} C_{r} x^{r}$ ...(ii)
Therefore $\frac{T_{r + 1}}{T_{r}}$
$= \frac{-^{n} C_{r} x^{r}}{^{n} C_{r - 1} x^{r - 1}}$
$= \frac{-^{n} C_{r} x}{^{n} C_{r - 1}}$
$= - \frac{(n - (r - 1)) x}{r}$
$= - \frac{(n - r + 1) x}{r}$

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