• # question_answer 77) The mean of discrete observations ${{y}_{1}},\,\,\,{{y}_{2}},\,\,\,{{y}_{3}},\,....,\,\,\,{{y}_{n}}$ is given by A) $\frac{\sum\limits_{i=1}^{n}{{{y}_{i}}}}{n}$                     B) $\frac{\sum\limits_{i=1}^{n}{{{y}_{i}}}}{\sum\limits_{i=1}^{n}{i}}$C) $\frac{\sum\limits_{i=1}^{n}{{{y}_{i}}}{{f}_{i}}}{n}$                      D) $\frac{\sum\limits_{i=1}^{n}{{{y}_{i}}}{{f}_{i}}}{\sum\limits_{i=1}^{n}{{{f}_{i}}}}$

$Lf'(0)=\underset{h\to {{0}^{-}}}{\mathop{Lt}}\,\frac{f(0+h)-f(0)}{h}=\underset{h\to {{0}^{-}}}{\mathop{Lt}}\,\frac{-{{h}^{2}}-0}{h}=0$ &$Rf'(0)=\underset{h\to {{0}^{+}}}{\mathop{Lt}}\,\frac{f(0+h)-f(0)}{h}=\underset{h\to {{0}^{+}}}{\mathop{Lt}}\,\frac{+{{h}^{2}}}{h}=0$ Hence, $f(x)$ is differentiable at$x=0$