Đáp án:
$C=\frac{5}{19}\\
D=\frac{11}{34}\\
E=6$
Giải thích các bước giải:
$C=(\frac{4}{3}+\frac{8}{3}).(\frac{7}{4}-\frac{6}{4}):(\frac{6}{5}+\frac{12}{5}+\frac{1}{5})\\
=\frac{12}{3}.\frac{1}{4}:\frac{6+12+1}{5}\\
=4.\frac{1}{4}.\frac{5}{19}\\
=\frac{5}{19}\\
D=\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+...+\frac{1}{31.34}\\
=\frac{1}{3}.(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{31.34})\\
=\frac{1}{3}.(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{31}-\frac{1}{34})\\
=\frac{1}{3}.(1-\frac{1}{34})\\
=\frac{1}{3}.(\frac{34}{34}-\frac{1}{34})\\
=\frac{1}{3}.\frac{33}{34}\\
=\frac{11}{34}\\
E=\frac{1.2}{1^2}.\frac{2.3}{2^2}.\frac{3.4}{3^2}.\frac{4.5}{4^2}.\frac{5.6}{5^2}\\
=2.\frac{3}{2}.\frac{4}{3}.\frac{5}{4}.\frac{6}{5}\\
=6$