=>2/1*3+2/3*5+...+2/(2x-1)(2x+1)=98/99
=>1-1/3+1/3-1/5+...+1/(2x-1)-1/(2x+1)=98/99
=>1-1/(2x+1)=98/99
=>1/(2x+1)=1/99
=>2x+1=99
=>x=49
\(\dfrac{1}{1.3}\) + \(\dfrac{1}{3.5}\) + \(\dfrac{1}{5.7}\) +......+ \(\dfrac{1}{(2x-1)(2x+1)}\) = \(\dfrac{49}{99}\)
HeLp me
BT1: Tìm x\(\in\)N * :
\(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{\left(2x+1\right)\cdot\left(2x+3\right)}\)=\(\frac{49}{99}\)
tim x biet 1/1.3 + 1/3.5+1/5.7+...+1/x.(x+2)=20/41
Tìm x biết 1/1.3+1/3.5+1/5.7+...+1/x.(x+2)=1005/2011
( 1/1.3+1/3.5+1/5.7+1/7.9+1/9.11). X = 2/3
Tìm x
1 phần 1.3 + 1 phần 3.5+ 1 phần 5.7+..+1 phần x+(X+2)=1005 phần 2011
tìm x
1/1.3 + 1/3.5 + 1/5.7 + ... + 1/x.(x+2) = 30/61
Tìm sốtựnhiên x biết: \(\dfrac{1}{1.3}+\dfrac{1}{3.5}+\dfrac{1}{5.7}+....+\dfrac{1}{x.\left(x+2\right)}=\dfrac{20}{41}\)
tìm x biết x/1.3+x/3.5+x/5.7+.........+x/97.99=49/99
