\(A=\frac{4}{4.5}+\frac{4}{5.6}+\frac{4}{6.7}+...+\frac{4}{47.48}\)
\(A=4.\left(\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+......+\frac{1}{47.48}\right)\)
\(A=4.\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+.....+\frac{1}{47}-\frac{1}{48}\right)\)
\(A=4.\left(\frac{1}{4}-\frac{1}{48}\right)\)
\(A=4.\frac{11}{48}\)
\(A=\frac{11}{12}\)
Tính tổng: \(A=\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+...+\frac{1}{49.50}\)
Bài 1. Tính nhanh nếu có thể:
A = 1 + 2 + 3 + 4 + 5 + ... + 99 + 100
B = \(\frac{1}{1.2}\)+ \(\frac{1}{2.3}\)+\(\frac{1}{3.4}\)+\(\frac{1}{4.5}\)+\(\frac{1}{5.6}\)+ ... +\(\frac{1}{99.100}\)
Tính \(\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+...+\frac{1}{49.50}\)
Tính A = \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+......+\frac{1}{99.100}=?\)
Tính nhanh:
C=\(\frac{7}{3.4}\)-\(\frac{9}{4.5}\)+\(\frac{11}{5.6}\)-\(\frac{13}{6.7}\)+\(\frac{15}{7.8}\)-\(\frac{17}{8.9}\)+\(\frac{19}{9.10}\)
tính nhanh
\(\frac{1}{5.6}\)+\(\frac{1}{6.7}\)+........+\(\frac{1}{19.20}\)
dau . là dấu nhân
Tìm X:
\(\frac{50+\frac{50}{3}+\frac{25}{3}+\frac{20}{4}+\frac{10}{3}+\frac{100}{6.7}+...+\frac{100}{98.99}+\frac{1}{99}}{\left(2x-1\right)}\)=11
tính nhanh
\(a.\frac{4}{3x7}+\frac{4}{7x11}+\frac{4}{11x15}+\frac{4}{15x19}+\frac{4}{19x23}+\frac{4}{23xx27}\)
TÍNH BẰNG CÁCH THUẬN TIỆN NHẤT
A)\(\frac{2}{3}\cdot\frac{4}{5}+\frac{1}{3}\cdot\frac{4}{5}=\)
B)\(\frac{1}{2}:\frac{3}{4}+\frac{1}{6}:\frac{3}{4}=\)
C)\(\frac{2}{3}\cdot\frac{4}{5}-\frac{1}{3}\cdot\frac{4}{5}=\)
D)\(\frac{1}{2}:\frac{3}{4}-\frac{1}{6}:\frac{3}{4}=\)
