A = 4 / 15.19+ 4/ 19.23 +.......+ 4/ 399.403
=1/15-1/19+1/19-1/23+...+1/399-1/403
=1/15-1/403
=403/6045-15/6045
=388/6045
=>A=388/6045
ruj quy đồng so sánh
cho A = 4 / 15.19+ 4/ 19.23 +.......+ 4/ 399.403 .chứng minh 16/81 < A < 16/80
Cho A= 4/15.19+4/19.23+...+4/399.403 chứng minh 16/81<A<16/80
Cho A = 4/15.19 + 4/19.23 + .....+ 4/399.403 chứng minh 16/81 < A < 16/80
cho A = 4/15.19 +4/19.23 +...+4/399.403 chứng minh 16/81 < A <16/80
tính hộ mik vs
cho A = 4 / 15.19+ 4/ 19.23 +.......+ 4/ 399.403 .chứng minh 16/81 < A < 16/80
\(Cho:A=\frac{4}{15.19}+\frac{4}{19.23}+...+\frac{4}{399.403}\)
Chứng minh: \(\frac{16}{81}\)< A< \(\frac{16}{80}\)
Cho \(A=\frac{4}{15.19}+\frac{4}{19.23}+...+\frac{4}{399.403}.\) Chứng minh răng: \(\frac{16}{81}< A< \frac{16}{80}\)
\(\frac{4}{3.7}+\frac{4}{7.11}+\frac{4}{11.15}+\frac{4}{15.19}+\frac{4}{19.23}+\frac{4}{23.27}\)
Cho A= 1/4 + 1/9 + 1/16 +...+ 1/81 + 1/100
Chứng minh A > 64/135
