\(B=\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^{2004}}+\frac{1}{3^{2005}}\)
\(\Rightarrow3B=1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^{2003}}+\frac{1}{3^{2004}}\)
\(\Rightarrow3B-B=1-\frac{1}{3^{2005}}\)
\(\Rightarrow2B=1-\frac{1}{3^{2005}}\)
\(\Rightarrow B=\frac{1-\frac{1}{3^{2005}}}{2}\)
thuc hien phep tinh (1-1/(1+2)).(1-1/(1+2+3))...(1-1/(1+2+3+...+2006))
thuc hien phep tinh :M=1+1/2(1+2)+1/3(1+2+3)+1/4(1+2+3+4)+...+1/16(1+2+3+...+16)
thuc hien phep tinh
a)(-3/7)^21 : (9/49)^6
b)3-(-67)^0+(1/2)^2 :2
thuc hien phep tinh:
P=(1/2-1*1/3-1*1/4-1*...1/2017-1*1/2018-1)
Thuc hien phep tinh:
a.3/7.11/15+3/7:15/14+2/7
b.(-7/15).5/8.15/-7(-32)
c.[(1/9:8/27):-1/3]:81/128
d.-66(1/2-1/3+1/11)+124(-37)+63(-124)
Thuc hien phep tinh
\(A=\left(1-\frac{1}{1+2}\right).\left(1-\frac{1}{1+2+3}\right)....\left(1-\frac{1}{1+2+3+...+2006}\right)\)
tim x biet,
5x + 5x+2= 650
Thuc hien phep tinh
(1+2+3+4+...+90).(12.34 - 6.68) : (1/3+1/4+1/5+1/6)
thuc hien phep tinh (Tinh nhanh neu co the)
(-5/12+7/4-3/8)-|4 va 1/2 -7 va 1/2|-( 1/4-5/2)
Thuc hien phep tinh :1 + 5 + 52 + 53 + 54 + ....+ 52015
