Bài 1: Chứng minh rằng:
a) $\frac{1}{6}$ + $\frac{1}{7}$ + $\frac{1}{8}$ + ...+ $\frac{1}{18}$ < 2
b) $\frac{1}{10}$ + $\frac{1}{11}$ + $\frac{1}{12}$ + ... + $\frac{1}{100}$ > 1
Bài 2: Tính hợp lí:
a) $\frac{1}{21}$ + $\frac{1}{77}$ + $\frac{1}{165}$ + $\frac{1}{285}$ + $\frac{1}{437}$ + $\frac{1}{621}$
b) $\frac{4}{21}$ + $\frac{4}{77}$ + $\frac{4}{165}$ + $\frac{4}{285}$ + $\frac{4}{437}$ + $\frac{4}{621}$
c)$\frac{1}{1.6}$ + $\frac{1}{6.11}$ + $\frac{1}{11.16}$ + $\frac{1}{16.21}$ + $\frac{1}{21.26}$ + $\frac{1}{26.31}$
d) $\frac{1}{4}$ + $\frac{1}{28}$ + $\frac{1}{70}$ + $\frac{1}{130}$ + $\frac{1}{208}$ + $\frac{1}{304}$
Bài 3: Tìm x:
a) $\frac{3}{2}$ .x + $\frac{3}{2}$ = x -$\frac{3}{4}$
b) $\frac{3}{2}$ .( x - $\frac{5}{3}$) - $\frac{4}{5}$ = x + 1
Loga
Sinh Học lớp 12
