Câu hỏi 8
Tính $A-B$, với
$$A=\frac{3}{1\times2}+\frac{7}{3\times4}+\frac{11}{5\times6}+\frac{15}{7\times8},\qquad B=\frac{5}{2\times3}+\frac{9}{4\times5}+\frac{13}{6\times7}.$$
$$A=\frac{3}{1\times2}+\frac{7}{3\times4}+\frac{11}{5\times6}+\frac{15}{7\times8},\qquad B=\frac{5}{2\times3}+\frac{9}{4\times5}+\frac{13}{6\times7}.$$