Data/2023/ex03notebookBanswer

$$\begin{aligned} \sum_{n=1}^{4}x_n &= x_1 + x_2 + x_3 + x_4 \\ &= 10 + 20 + 30 + 40 = 100\\ \sum_{n=5}^{8}x_n &= x_5 + x_6 + x_7 + x_8\\ &= 50 + 60 + 70 + 80 = 260 \end{aligned}$$

$$(\mbox{与式}) = x_1^2 + x_2^2 + x_3^2 = 100+400+900 = 1400$$

$$\begin{aligned} (\mbox{与式}) &= \sum_{n=1}^{4}x_n + \sum_{n=1}^{4}\pi = 100 + (\pi + \pi + \pi + \pi) = 100+4\pi \end{aligned}$$

$$(\mbox{与式}) = 2\sum_{n=1}^{4} x_n = 2\times 100 = 200$$

$$\begin{aligned} (\mbox{与式}) = a\sum_{n=1}^{4}x_n + \sum_{n=1}^{4}b = 100a + 4b \end{aligned}$$