Câu hỏi 23
Tính giá trị biểu thức sau
$$\left(\frac12+\frac13+\cdots+\frac1{30}\right)+\left(\frac23+\frac24+\cdots+\frac2{30}\right)+$$
$$\left(\frac34+\frac35+\cdots+\frac3{30}\right)+\cdots+\left(\frac{28}{29}+\frac{28}{30}\right)+\left(\frac{29}{30}\right).$$
$$\left(\frac12+\frac13+\cdots+\frac1{30}\right)+\left(\frac23+\frac24+\cdots+\frac2{30}\right)+$$
$$\left(\frac34+\frac35+\cdots+\frac3{30}\right)+\cdots+\left(\frac{28}{29}+\frac{28}{30}\right)+\left(\frac{29}{30}\right).$$