\(S=1+\frac{1}{3}+\frac{1}{6}+...+\frac{1}{45}\)
\(S=2.\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{90}\right)\)
\(S=2.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{9.10}\right)\)
\(S=2.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(S=2.\left(1-\frac{1}{10}\right)\)
\(S=2.\frac{9}{10}\)
\(S=\frac{9}{5}\)
So sanh S voi 2 biet: S=1+1/3+1/6+1/10+...+1/45
B=1/3+1/6+1/10+1/15+....+1/45
1/3 + 1/6 + 1/10 + 1/15 + ......+ 1/45
Đúng ghi Đ,sai ghi S điền vào chỗ trống:
a) 2 1/6 giờ = 2,6 giờ
b) 2 1/6 giờ = 2 giờ 10 phút
c) 3,45 giờ = 3 giờ 45 phút
d) 3,45 giờ = 3 giờ 27 phút
A=1+1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45
1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45
A= 1/3 + 1/6 + 1/10 + 1/15 + 1/21 +1/28 + 1/36 +1/45 + 1/55
tính:
1 + 3 + 6 + 10 +....+ 45 + 55/ 1 x 10 + 2 x 9 + 3 x 8 +...+ 8 x 3 + 9 x 2 + 10 x 1
Tìm A biết : A = 1/3 + 1/6 + 1/10 1/15 + ........ + 1/ 45 .
