Mathematics - Sequence & Series Question with Solution | TestHub

$S_r=\mathrm{r}/[1-1/(\mathrm{r}+1)]=\mathrm{r}+1$. A follows from the sum and B from the product $2\cdot 3\cdot \dots \cdot (\mathrm{n}+1)=(\mathrm{n}+1)!;\mathrm{C}$ telescopes $1/[(\mathrm{r}+1)(\mathrm{r}+2)]=1/(\mathrm{r}+1)-1/(\mathrm{r}+2)$. D is not an identity in n.