Tính tổng :\(S=1+\frac{1}{2}.\left(1+2\right)+\frac{1}{3}.\left(1+2+3\right)+\frac{1}{4}.\left(1+2+3+4\right)+....+\frac{1}{50}.\left(1+2+3+4+....+50\right)\)
tính A biết
A=\(\dfrac{1}{1+2}\)+\(\dfrac{1}{1+2+3}\)+\(\dfrac{1}{1+2+3+4}\)+...+\(\dfrac{1}{1+2+3+...+50}\)
tính S = 1/1*2 + 1/ 2*3 + 1/3*4 + ....+ 1/ 49*50
Tính A=1/(1*2*3)+1/(2*3*4)+1/(3*4*5)+...+1/(48*49*50)
Tính nhanh:
1/1+2 + 1/ 1+2+3 + 1/1+2+3+4 + .....+ 1/1+2+3+4+....+50 = ?
Tính nhanh:
1/1+2 + 1/ 1+2+3 + 1/1+2+3+4 + .....+ 1/1+2+3+4+....+50 = ?
E=-1/3.(1+2+3)-1/4.(1+2+3+4)-...-1/50.(1+2+3+4+...+50)
Tính:
M=(1-1/2^2).(1-1/3^2).(1-1/4^2)...(1-1/49^2).(1-1/50^2)
N=(3/2-2/2^2).(4/3-2/3^2).(5/4-2/4^2)...(100/99-2/99^2).(101/100-2/100^2)