\(Cho:A=\frac{4}{15.19}+\frac{4}{19.23}+...+\frac{4}{399.403}\)
Chứng minh: \(\frac{16}{81}\)< A< \(\frac{16}{80}\)
Cho A=\(\frac{4}{15.19}\)+\(\frac{4}{19.23}\)+...+\(\frac{4}{399.403}\)
CMR \(\frac{16}{81}\)<A<\(\frac{16}{80}\)
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
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
ko bít làm đâu nha.ahihi
Cho A= 4/15.19+4/19.23+...+4/399.403 chứng minh 16/81<A<16/80
\(\Leftrightarrow A=\frac{1}{15}-\frac{1}{19}+\frac{1}{19}-\frac{1}{23}+...+\frac{1}{399}-\frac{1}{403}\)
\(\Rightarrow A=\left(\frac{1}{15}-\frac{1}{403}\right)=0,0\left(6418...\right)\)
MÀ 16/81=0,(197530864<0,0(64..)<16/80=0,2
=>(đpcm)
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/ 23.27 +...+ 4/ 399.403. Chứng minh 16/81< A < 8/9
sai de ah
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