a, [(4.x+28):3+55]:5=35
b, (2/3.5+2/5.7+2/7.9+.....+2/19.21).x=9/7
tìm x
Những câu hỏi liên quan
Tính A=2/1.3-4/3.5+6/5.7-8/7.9+...-20/19.21
Tìm x:3/3.5+3/5.7+3/7.9+...+x.(x+2)=8/9
1/3.5+1/5.7+1/7.9+...+1/(2.x+1)(2.x+3)=5/31
1/3.5+1/5.7+1/7.9+...+1/(2x+1)(2x+3)=5/31
1/2(2/3.5+2/5.7+2/7.9+...+2/(2x+1)(2x+3))=5/31
1/3-1/5+1/5-1/7+1/7-1/9+...+1/2x+1-1/2x+3=5/31:1/2
1/3-1/2x+3=10/31
1/2x+3=1/3-10/31
1/2x+3=1/63
suy ra : 2x+3=63
2x=63-3
2x=60
x=60:2
x=30
vay x=30
nhớ **** cho mình nha
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bài 1
a,-1/8 - (320% + 9/5 ) . (1/4 - 1/8
b,4/3.5 + 4/5.7 + 4/7.9 + ......+4/99.100
bài 2
a,x+ 3/22 = 27/121.11/9
Đặt \(A=\frac{4}{3.5}+\frac{4}{5.7}+\frac{4}{7.9}+...+\frac{4}{99.101}\)
\(\Rightarrow\frac{1}{2}A=\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{99.101}\)
\(\Rightarrow\frac{1}{2}A=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{99}-\frac{1}{101}\)
\(\Rightarrow\frac{1}{2}A=\frac{1}{3}-\frac{1}{101}\)
\(\Rightarrow\frac{1}{2}A=\frac{101}{303}-\frac{3}{303}\)
\(\Rightarrow\frac{1}{2}A=\frac{98}{303}\)
\(\Rightarrow A=\frac{98}{303}\div\frac{1}{2}\)
\(\Rightarrow A=\frac{199}{303}\)
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\(x+\frac{3}{22}=\frac{27}{121}.\frac{11}{9}\)
\(\Leftrightarrow x+\frac{3}{22}=\frac{27.11}{121.9}\)
\(\Leftrightarrow x+\frac{3}{22}=\frac{3.1}{11.1}\)
\(\Leftrightarrow x+\frac{3}{22}=\frac{3}{11}\)
\(\Leftrightarrow x=\frac{3}{11}-\frac{3}{22}\)
\(\Leftrightarrow x=\frac{6}{22}-\frac{3}{22}\)
\(\Leftrightarrow x=\frac{3}{22}\)
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1) Tìm x
a) (1/4 x X - 1/8) x 3/4 = 1/4
b) 12/5 : X = 14/3 x 4/7
c) x + 2/3 = 8 : 4 - 1
2) Thực hiện phép tính:
a) (1/5 + 3/4) x 1/2
b) 13/20 - (1/4 - 5/20)
c) 1/10 + 4/20 + 9/30 + 25/50 + 36/60 + 49/70 + 64/80 + 81/90
d) 2/3.5 + 2/5.7 + 2/7.9 + ... + 2/41.43
Cho A = 2/1.3 + 2/3.5 + 2/5.7 + 2/7.9 +.....+ 2/97.99 và B = 1^2 / 1.2 x 2^2/2.3 x 3^2 / 3.4 x 4^2 /4.5 x .... x 98^2 / 98.99. Chứng tỏ A = 98B
Ta có :\(B=\frac{1^2}{1.2}.\frac{2^2}{2.3}.\frac{3^2}{3.4}.\frac{4^2}{4.5}.....\frac{98^2}{98.99}=\frac{\left(1.2.3.4...98\right).\left(1.2.3.4...98\right)}{\left(1.2.3.4...98\right).\left(2.3.4.5...99\right)}=\frac{1}{99}\)
Lại có A = \(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{97.99}=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{97}-\frac{1}{99}=1-\frac{1}{99}=\frac{98}{99}\)
Lại có \(A:B=\frac{98}{99}:\frac{1}{99}=98\)
=> A = 98B
các bạn có về sweet home
Tìm x, biết: 1/3 + 1/3.5 + 1/5.7 + 1/7.9 +...+ 1/(x+2).(x+4)=50/101
<=> 2/1.3 + 2/3.5 + 2/5.7 +....+ 2/(x+2)(x+4) = 100/101
<=> 1 - 1/3 + 1/3 - 1/5 + 1/5 - 1/7 +.....+ 1/x+2 - 1/x+4 = 100/101
<=> 1 - 1/x+4 = 100/101
<=> 1/x+4 = 1 - 100/101 <=> 1/x+4 = 1/101 <=> x+4 = 101 <=> x= 101 - 4 = 97
:)
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típ nha m.n18) (2+x ) +(4+x)+(6+x )+...+(52+x) 780(1/3.5 +1/5.7+1/7.9 +...+1/19.21).x 9/720) (x+1)+(x+2)+...+(x+100)575022) (x+1/1.3)+(x.1/3.5)+(x+1/5.7)+...+(x+23.25) 11.x+(1/3+1/9+1/27+1/81+1/243 )23) (1/1.2.3 +1/2.3.4+....+1/8.9.10).x 23/45 sqrt{ }
Đọc tiếp
típ nha m.n
18) (2+x ) +(4+x)+(6+x )+...+(52+x) = 780
(1/3.5 +1/5.7+1/7.9 +...+1/19.21).x = 9/7
20) (x+1)+(x+2)+...+(x+100)=5750
22) (x+1/1.3)+(x.1/3.5)+(x+1/5.7)+...+(x+23.25)= 11.x+(1/3+1/9+1/27+1/81+1/243 )
23) (1/1.2.3 +1/2.3.4+....+1/8.9.10).x= 23/45
| \(\sqrt{ }\) | |||||||
\(\left(2+x\right)+\left(4+x\right)+\left(6+x\right)+...+\left(52+x\right)=780\)
\(\Leftrightarrow26x+\left(2+4+6+...+52\right)=780\)
\(\Leftrightarrow26x+\left[\left(52+2\right).26:2\right]=780\)
\(\Leftrightarrow26x+702=780\)
\(\Leftrightarrow26x=78\)
\(\Leftrightarrow x=\frac{78}{26}=3\)
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(2+x)+(4+x)+(6+x)+...+(52+x)=780
⇔26x+(2+4+6+...+52)=780
⇔26x+[(52+2).26:2]=780
⇔26x+702=780
⇔26x=78
⇔x=7826 =3
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1/3.5 +1/5.7+1/7.9+...+1/(2.x+1).(2.x+3)
Tìm x