1938.(1/2.5+1/5.8+1/8.11+...+1/17.20)
= 1938.3/3(1/2.5+1/5.8+1/8.11+...+1/17.20)
= 1938/3.(3/2.5+3/5.8+3/8.11+...+3/17.20)
= 1938/3.(1/2-1/5+1/5-1/8+1/8-1/11+1/11+...+1/17-1/20)
= 1938/3.(1/2-1/20)
= 1938/3.9/20
= 2907/10
(1/2.5 +1/5.8 + 1/811+...+1/17.20)
Tính S
S=1/2.5+1/5.8+1/8.11+1/11.14+1/14.17+1/17.20
Tính tổng sau:
\(S=\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+....+\frac{1}{17.20}\)
giải giúp mình nka
\(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+\frac{1}{14.17}+\frac{1}{17.20}\)
Tính tổng :
M= 4/2.5 + 4/5.8 + 4/8.11 + 4/11.14 + 4/14.17 + 4/17.20
so sánh A với 1 , biếtA = \(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+\frac{1}{14.17}+\frac{1}{17.20}\)
S=\(\frac{1}{2.5}\)+\(\frac{1}{5.8}\)+...+\(\frac{1}{17.20}\)
tinh nhanh
Tính:
A=3/2.5+3/5.8+....+3/17.20
Tính nhanh :
P= 3/2.5 +3/5.8 +3/8.11 +....+3/17.20