68+1/3+1/6+1/10+1/15+...+1/190
X * ( 1 + 1/3 + 1/6 + 1/10 + 1/15 + ...... + 1/190 )
Tìm x biết : X x (1+1/3+1/6+1/10+1/15+...+1/190)=2013x19/10
P=(1-1/3).(1-1/6).(1-1/10).(1-1/15)...(1-1/190)
Tính P=(1-1/3)*(1-1/6)*(1-1/10)*(1-1/15)*...*(1-1/190)
tính giá trị biểu thức : P= (1-1/3).(1-1/6).(1-1/10).(1-1/15)...(1-1/190)
Tính A=1/3+1/6+1/10+1/15+....+1/171+1/190
Các bn giúp mk nhé
Cảm ơn
=2*(1/6+1/12+1/20+...+1/380)
=2*(1/2*3+1/3*4+1/4*5+...+1/19*20)
=2*(1/2-1/3+1/3-1/4+1/4-1/5+...+1/19-1/20)
=2*(1/2-1/20)
=2*(10/20-1/20)
=2*9/20
=18/20
=9/10
A/2=(1/3+1/6+1/10+1/15+...+1/171+1/190)/2
=1/6+1/12+1/20+1/30+...+1/342+1/380
=1/2.3+1/3.4+1/4.5+1/5.6+....+1/18.19+1/19.20
=1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 +....+ 1/18 - 1/19 + 1/19 - 1/20
=1/2 - 1/20 = 10/20 - 1/20 = 9/20
=> A = 9/20 .2 = 18/20=9/10
Cho A = \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+...+\frac{1}{190}\)
Tính A x 10
Cho A = \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+...+\frac{1}{190}\)
Tính A X 10
dạng chuỗi nha bạn
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TínhA=1/3+1/6+1/10+....+1/190
A:2 = 1/6 + 1/12 + 1/20 +...+ 1/380 = 1/(2x3) + 1/(3x4) + 1/(4x5) + ... + 1/(19x20) = 1/2 - 1/3+1/3 - 1/4 +....+ 1/19- 1/20 = 1/2 - 1/20 = 9/20 Suy ra A = 9/20 x 2 = 9/10