2/10+2/40+2/88+.....+2/340+2/460
=2/2.5+2/5.8+2/8.11+....+2/17.20+2/20.23
=2/3.(3/2.5+3/5.8+3/8.11+....+3/17.20+3/20.23)
=2/3.(1/2-1/5+1/5-1/8+1/8-1/11+.....+1/17-1/20+1/20-1/23)
=2/3.(1/2-1/23)=2/3.21/46=7/23
cho mình xin 1 ks
2/10+2/40+2/88+...+2/340+2/460=
2/10+2/40+2/88+...+2/340+2/460
Thực hiện phép tính :
2/10+2/40+...+2/340+2/460
tính nhanh;A= 3^2/10+3^2/40+3^2/88+...+3^2/340
Tính nhanh tổng : F=42/10+42/40+42/88+....+42/340
tính :
\(\frac{3^2}{10}+\frac{3^2}{40}+\frac{3^2}{88}+...+\frac{3^2}{340}\)
ai làm nhanh nhất mk sẽ tk cho bạn đó nha!
11/10+41/40+89/88+...+461/460
\(A=\frac{1}{1.3}\)\(+\frac{1}{3.5}\)\(+\frac{1}{5.7}\)\(+...+\frac{1}{99.101}\)
\(A=\frac{3^2}{10}+\frac{3^2}{40}\)\(+\frac{3^2}{88}\)\(+...+\frac{3^2}{340}\)
Bài 1:Tính
1/10+1/40+1/88+1/154+1/238+1/340
Bài 2:Cho A=1/2 mũ 2+1/3 mũ 2+1/4 mũ 2+....+1/100 mũ hai.Chứng minh A<3/4
Bài 3:Tính nhanh giá trị biểu thức
B=1/3.5+1/5.7+...+1/47.49+1/49.51
A=1+1/2+1/2 mũ 2+1/2 mũ 3+...+1/2 mũ 2010
