A=1/8+1/24+1/48+1/80+...+1/440
\(ChoB=\left(80-\frac{1}{9}-\frac{2}{10}-\frac{3}{11}-....-\frac{80}{88}\right):\left(\frac{1}{45}+\frac{1}{50}+\frac{1}{55}+...+\frac{1}{440}\right)\)
P = 1 1/3 x 1 1/8 x 1 1/15 x 1 1/24 x 1 1/35 x 1 1/48 x 1 1/63 x 1 1/80 x 1 1/99
Tính nhanh:
\(B=\left(1+\frac{1}{8}\right)\)x \(\left(1+\frac{1}{15}\right)\)x \(\left(1+\frac{1}{24}\right)\)x........ x \(\left(1+\frac{1}{440}\right)\)x \(\left(1+\frac{1}{483}\right)\)
Tính nhanh:
a,1/4+2/5+6/8+9/15+8/1
b,1/2+2/4+3/6+4/8+5/10+6/12+7/14+8/16+9/18+10/20
c,1/10+4/20+9/30+16/40+25/50+36/60+49/70+64/80+81/90
Tính nhanh:
a,1/4+2/5+6/8+9/15+8/1
b,1/2+2/4+3/6+4/8+5/10+6/12+7/14+8/16+9/18+10/20
c,1/10+4/20+9/30+16/40+25/50+36/60+49/70+64/80+81/90
d. 1/8, 1/24, 1/48, 1/80, ...
e. 1/21,1/77,1,165, 1/285Nêu quy luật tìm số hạng thứ 20 của dãy :
a. 9, 10, 12, 15, 19, ...
b. 67, 71, 75, 79, ...
c.5, 12, 21, 32, ...
ai giúp em câu này đi
a,6/1*3*7+6/3*7*9+6/7*9*13+6/9*13*15+6/13*15*19
b,1/1*3*7+1/3*7*9+1/7*9*13+1/9*13*15+1/13*15*19
c,1/2*4*6+1/4*6*8+1/6*8*10+1/8*10*12*14+...+1/96*98*100
d,5/1*5*8+5/5*8*12+5/8*12*15+...+5/33*36*40
* là dấu nhân / là phần nha
Nêu quy luật tìm số hạng thứ 20 của dãy :
a. 9, 10, 12, 15, 19, ...
b. 67, 71, 75, 79, ...
c.5, 12, 21, 32, ...
d. 1/8, 1/24, 1/48, 1/80, ...
e. 1/21,1/77,1,165, 1/285
