A = 1/1.4 + 1/4.7 + 1/7.10 + ... + 1/97.100
3A = 3/1.4 + 3/4.7 + 3/7.10 + ... + 3/97.100 = (4-1)/1.4 + (7-4)/4.7 + (10-7)/7.10 + ... + (100-97)/97.100
= 1/1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/97 - 1/100 = 1 - 1/100 = 99/100
=> A = 33/100
A = x/2 => x = 2.A = 33/50
tính tổng : 1x4 + 2x5 + .... + 97x100
1x4+4x7+7x10+...+2022x2023
gúp với
cần gấp
Tìm x
a/ x 2 − 3 x 5 − 13 5 = − 7 5 + 7 x 10
b/ x 2 .3 + x 3 .4 + x 4 .5 + . .. + x 99 .100 = − 1
1/1.4 + 1/4.7 + 1/7.10 ... + 1/x.(x+3) = 125/376
Tìm x:
1/1.4 + 1/4.7 + 1/7.10 + ... + 1/x.(x+3)= 667/2002
\(\dfrac{1}{1.4}+\dfrac{1}{4.7}+\dfrac{1}{7.10}+.......+\dfrac{1}{x\left(x+3\right)}=\dfrac{125}{376}\)(x ϵ N*)
Tìm x :
1/1x4+1/4x7+...+1/2002x2005
tìm x thuộc N*
a)1/1.4 + 1/4.7 +1/7.10 +........+ 1/x.(x+3) = 49/148
1.
a) 1/1.4+1/4.7+1/7.10+...+1/100.103
b)-1/3+-1/15+-1/35+-1/63+...+-1/9999
2.
3/1.4+3/4.7+3/7.10+...+3/94.97+3/97.100
