=\(1\left(\frac{1}{14.15}+\frac{1}{15.19}+......+\frac{1}{51.55}\right)\)
=\(1\left(\frac{1}{14}-\frac{1}{15}\right)+\left(\frac{1}{15}-\frac{1}{19}\right).....+\left(\frac{1}{51}-\frac{1}{55}\right)\)
=\(1\left(\frac{1}{14}-\frac{1}{15}+\frac{1}{15}-\frac{1}{19}....+\frac{1}{51}-\frac{1}{55}\right)\)
=\(1\left(\frac{1}{14}-\frac{1}{55}\right)\)
=\(1.\frac{41}{770}\)
=\(\frac{41}{770}\)
\(ChoA=\frac{2}{11.15}+\frac{2}{15.19}+\frac{2}{19.23}+...+\frac{2}{51.55}\)
Tính A
Cho \(A=\frac{2}{11.15}+\frac{2}{15.19}+\frac{2}{19.23}+...+\frac{2}{51.55};B=\left(-\frac{5}{3}\right).\frac{11}{2}.\left(\frac{1}{3}+1\right)\)
Tính tích A.B
a) Cho A = \(\frac{2}{11.15}+\frac{2}{15.19}+\frac{2}{19.23}+....+\frac{2}{51.55}\). Tính tích A. B
b) Chứng tỏ rằng các số tự nhiên có dạng: abcabc chia hết cho ít nhất 3 số nguên tố
tính tích A>B biết:
\(A=\left(-\dfrac{5}{3}\right).5\dfrac{1}{2}.\left(\dfrac{1}{3}+1\right)\)
\(B=\dfrac{2}{11.15}+\dfrac{2}{15.19}+\dfrac{2}{19.23}+...+\dfrac{2}{51.55}\)
\(\frac{4}{3.7}+\frac{4}{7.11}+\frac{4}{11.15}+\frac{4}{15.19}+\frac{4}{19.23}+\frac{4}{23.27}\)
\(Cho:A=\frac{4}{15.19}+\frac{4}{19.23}+...+\frac{4}{399.403}\)
Chứng minh: \(\frac{16}{81}\)< A< \(\frac{16}{80}\)
\(\frac{2}{9.11}+\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.19}\)
Tính
2/11.15+2/15.19+......+2/51.55
Cho A=2/1115 +2/1519 +2/19.23 +...+2/51.55 ;B=(−5/3 ).11/2.(1/3+1)
Tính tích A.B
