Đáp án:
Giải thích các bước giải:
Bài 2: a/ $(7+\frac{7}{5}-\frac{2}{3})-(4+\frac{4}{5}+\frac{3}{8})+(3-\frac{3}{5}+\frac{2}{3}+\frac{3}{8})$
$=7+\frac{7}{5}-\frac{2}{3}-4-\frac{4}{5}-\frac{3}{8})+3-\frac{3}{5}+\frac{2}{3}+\frac{3}{8}$
$=(7-4+3)+(\frac{7}{5}-\frac{4}{5}-\frac{3}{5})+(-\frac{2}{3}+\frac{2}{3})+(-\frac{3}{8}+\frac{3}{8})$
$=6$
b/ $(-\frac{1}{2})+(-\frac{1}{9})-(-\frac{3}{5})+\frac{1}{2006}-(-\frac{2}{7}-\frac{7}{18}+\frac{4}{35}$
$=-\frac{1}{2}-\frac{1}{9}+\frac{3}{5}+\frac{1}{2006}+\frac{2}{7}-\frac{7}{18}+\frac{4}{35}$
$=(-\frac{1}{2}-\frac{1}{9}-\frac{7}{18})+(\frac{3}{5}+\frac{2}{7}+\frac{4}{35})+\frac{1}{2006}$
$=\frac{-9-2-7}{18}+\frac{21+10+4}{35}+\frac{1}{2006}$
$=-1+1+\frac{1}{2006}=\frac{1}{2006}$
c/ $\frac{1}{3}-\frac{3}{4}+\frac{3}{5}+\frac{1}{2007}-\frac{1}{36}+\frac{1}{15}-\frac{2}{9}$
$=(\frac{1}{3}+\frac{3}{5}+\frac{1}{15})+(-\frac{3}{4}-\frac{1}{36}-\frac{2}{9})+\frac{1}{2007}$
$=\frac{5+9+1}{15}+\frac{-27-1-8}{36}+\frac{1}{2007}$
$=1-1+\frac{1}{2007}=+\frac{1}{2007}$
d/ $\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+......+\frac{1}{2006.2007}$
$=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+......+\frac{1}{2006}-\frac{1}{2007}$
$=1-\frac{1}{2007}$
$=\frac{2006}{2007}$
Chúc bạn học tốt !!!
