ta có A= 6/2.5 + 6/5.8+...+ 6/47.50
=2x( 3/2x5 +3/5x8 +...+3/47x50)
=2x(1/2 - 1/5 + 1/5 - 1/8 + ... + 1/47 - 1/50)
=2x(1/2 - 1/50 ) =1-2/5= 5/5 -2/5 =3/5
bài này quá dễ
\(\frac{3}{2x5}\)+ \(\frac{3}{5x8}\)+ \(\frac{3}{8x11}\)+ ... + \(\frac{3}{\left(X-3\right)xX}\)= \(\frac{1}{6}\)
Giúp mk nhé!!!
Tính tổng
\(\frac{3^2}{2x5}+\frac{3^2}{5x8}\frac{3^2}{8x11}+......+\frac{3^2}{27x30}\)
Tính
a)S1=2/3x5+2/5x7+2/7x9+...+2/97x99
b)S2=6/2x5+6/5x8+6/8x11+...+6/29x32
\(\frac{3}{2x5}\)+ \(\frac{3}{5x8}\)+\(\frac{3}{8x11}\)+ ... + \(\frac{3}{\left(X-3\right)xX}\)
Giúp mk nhé!!!Thanks <3
Câu 1:Tìm a biết :
\(\frac{15,2x0,25-48,51:14,7}{a}\)=\(\frac{\left(\frac{13}{44}-\frac{2}{11}-\frac{5}{66}:2\frac{1}{2}\right)x1\frac{1}{5}}{3,2+0,8x\left(5\frac{1}{2}-3,25\right)}\)
Câu 2 :TÌM n
\(\frac{1}{2x5}\)+\(\frac{1}{5x8}\)+\(\frac{1}{8x11}\)+..........+\(\frac{1}{n\left(n+3\right)}\)=\(\frac{31}{198}\)
\(\frac{1}{5x8}+\frac{1}{8x11}+...+\frac{1}{Xx\left(X+3\right)}=\frac{101}{1540}\)
Help mình với
A=6/5x8+6/8x11+...+6/87x90
Bài 5 : Thực hiện phép tính :
4/5x8 + 4/8x11 +.....+ 4/ 47x50
