tim x biet : 1/3+1/6+1/10+1/15+...+2/x*(x+1) = 999/1000
Những câu hỏi liên quan
Tinh tong: a) 9 + 99 + 999 + ... + 999...999 ( co 10 c/s 9 )
b) Tim x, biet: 1/21 + 1/28 = 1/36 +... + 2/x(x+1) = 2 / 9
a,
=(10-1)+(10^2 - 1)+...+(10^10 - 1)
=(10 + 10^2 + 10^3 +....+ 10^10) - 10
=10^2+10^3+10^4+....+10^10
=11111111100
b,
1/21+1/28 ko bằng 2/9
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tim x, biet:
a,(3x-15)^7=0
b,4^2x-6=1
c,(3-x)^20:(3-x)^10=1(x khac 3)
d,(x-6)^3=(x-6)^2
a, Do \(\left[3x-15\right]^7=0\)
=> \(3x-15=0\)
=> \(3x=0+15\)
=> \(3x=15\)
=> \(x=15:3\)
=> \(x=5\)
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\(\left(3x-5\right)^7=0\)
\(\Rightarrow3x-5=0\)
\(\Rightarrow3x=5\)
\(\Rightarrow x=\frac{5}{3}\)
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tim stn x biet 1/3 + 1/6 + 1/10 +...+2/x x (x - 1) = 2005/2006
1 tim cac so nguyen x,y biet x/7=6/21 -5/y=20/28 1/2=x/12 x/8=-28/32 3/y=12/24 3/4=15/y 2 viet 3 phan so bang phan so -10/15
tim x biet :1/3+1/6+1/10=..+2/x.(x+1)=2001/2003
a)(1/2+1)x(1/3+1)x(1/4+1)x...x(1/999+1)
b)(1/2-1)x(1/3-1)x(1/4-1)x...x(1/1000-1)
c)3/22 x 8/32 x 15/42 x .... x 99/102
help me please
Vậy xét là \(\frac{1}{2}+1\)nhé.
a,\(\frac{3}{2}x\frac{4}{3}x\frac{5}{4}x...x\frac{1000}{999}\)
=3x4x5x...x1000/2x3x4x...x999
=1000/2=500
b, c tương tự câu a
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)(1/2+1)x(1/3+1)x(1/4+1)x...x(1/999+1)
b)(1/2-1)x(1/3-1)x(1/4-1)x...x(1/1000-1)
c)3/22 x 8/32 x 15/42 x .... x 99/102
mình ko biết làm chép lại de thui
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Xem thêm câu trả lời
tim x thuoc N biet 1/3+1/6+1/10...+1/x.(x+1) :2=2001/2003
\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+....+\frac{1}{x\left(x+1\right):2}=\frac{2001}{2003}\)
\(\frac{2}{6}+\frac{2}{12}+\frac{2}{20}+....+\frac{2}{x\left(x+1\right)}=\frac{2001}{2003}\)
\(2\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+....+\frac{1}{x\left(x+1\right)}\right)=\frac{2001}{2003}\)
\(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+....+\frac{1}{x}-\frac{1}{x+1}=\frac{2001}{2003}:2=\frac{2001}{4006}\)
\(\frac{1}{2}-\frac{1}{x+1}=\frac{2001}{4006}\)
\(\frac{1}{x+1}=\frac{1}{2}-\frac{2001}{4006}=\frac{1}{2003}\)
=> x+1 = 2003
=> x = 2003 - 1
=> x = 2002
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Tim x biet: 1/10+1/15+1/21+.........+2/x.(x+1) = 2010/2012
tim x biet :
a) 1/3 + 1/6 +1/10+ ...+ 2/ x*(x+1)
b) 1/2 + 1/6 +1/12 + ...+1/x=72/73