\(\frac{4}{21}+\frac{4}{77}+\frac{4}{165}+...+\frac{4}{11877}\)
\(=\frac{4}{3.7}+\frac{4}{7.11}+\frac{4}{11.15}+...+\frac{4}{107.111}\)
\(=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{15}+...+\frac{1}{107}-\frac{1}{111}\)
\(=\frac{1}{3}-\frac{1}{111}\)
\(=\frac{111}{333}-\frac{3}{333}=\frac{108}{333}=\frac{12}{37}\)
Tinh tong sau bang cach hop li nhat: (1+3+5+...+99)-(2+4+6+...+100)
\(D=\frac{4}{21}+\frac{4}{77}+\frac{4}{165}+\frac{4}{285}+\frac{4}{437}+\frac{4}{621}\)
1/2+1/4+1/16+.....+1/100000
tinh cac tong sau 1 cach hop li
tinh tong sau bang cach hop ly
a = 2+2^2+2^3+2^4+...+2^100
mong moi nguoi giup do
tinh bang cach hop li nếu có thể toán 6
(-1/5+3/12) +-3/4
-1/2+3/21+2/-6+5/-30
Tính hợp lí:
a) A = \(\dfrac{1}{56}\) + \(\dfrac{1}{72}\) + \(\dfrac{1}{90}\) + \(\dfrac{1}{110}\) + \(\dfrac{1}{132}\) + \(\dfrac{1}{156}\) ;
b) B = \(\dfrac{4}{21}\) + \(\dfrac{4}{77}\) + \(\dfrac{4}{165}\) + \(\dfrac{4}{285}\) +\(\dfrac{4}{437}\) +\(\dfrac{4}{621}\);
c) C = \(\dfrac{1}{21}\) + \(\dfrac{1}{77}\) +\(\dfrac{1}{165}\) +\(\dfrac{1}{285}\) +\(\dfrac{1}{437}\) +\(\dfrac{1}{621}\) ;
d) D = \(\dfrac{1}{1.6}\) + \(\dfrac{1}{6.11}\) +\(\dfrac{1}{11.16}\) +\(\dfrac{1}{16.21}\) +\(\dfrac{1}{26.31}\) .
cho tap hop F co cac so tu nhien co 2 chu so ma tong cac chu so = 4 ai tra loi gap
ghi bang 2 cach liet ke va tong hop
tinh bang cach hop li
(-8).25.(-375).(-4).125
(-19).8+(-19).(-3)
(-137)+76.(-137)+(-137).23
24.(-21)+(-121).(-24)
Tinh cac tong sau day mot cach hop li:
a) A= 1+ 5+ 52+ 53+........+ 51998
b) B= 1+ 4+ 42 + .................+ 4 n
