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5x+2 - 5x = 6 . 102
5x . 52 - 5x = 6 . 100
5x . ( 52 - 1 ) = 600
5x . 24 = 600
5x = 600 : 24
5x = 25
5x = 52
=> x = 2
Vậy x = 2
_HT_
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23 - x : 2 + 6 . 10 = 68
23 - x : 2 + 60 = 68
23 - x : 2 = 68 - 60
23 - x : 2 = 8
x : 2 = 23 - 8
x : 2 = 15
x = 15 x 2
x = 30
23 - x : 2 + 6 . 10 = 68
23 - x : 2 + 60 = 68
23 - x : 2 = 68 - 60
23 - x : 2 = 8
x : 2 = 23 - 8
x : 2 = 15
x = 15 x 2
x = 30
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Bài 1:
a) 6/2 x+ 1 = 2/7
6/2 x = 2/7 - 1
6/2 x = 2/7 - 7/7
6/2 x = -5/7
x = - 5/7 : 6/2
x = - 5/7 . 2/6
x = -5/21
Ủng hộ nha! :)
BÀI 1 a 6/2x+1=2/7
6/2x=2/7-1
6/2x=-5/7
6*7=5*2x
42=5*2x
42/5=2x
x=42/5:2
x=21/5
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Gọi tổng trên là A.Ta có
\(A=\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}+\frac{1}{143}+\frac{1}{195}\)
\(2A=\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+\frac{2}{99}+\frac{2}{143}+\frac{2}{195}\)
\(2A=\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+\frac{2}{11.13}+\frac{2}{13.15}\)
\(2A=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}\)
\(2A=\frac{1}{3}-\frac{1}{15}\)
\(2A=\frac{5}{15}-\frac{1}{15}\)
\(2A=\frac{4}{15}\)
\(A=\frac{4}{15}:2\)
\(A=\frac{2}{15}\)
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Bài 2:
Ta có:\(\dfrac{x+46}{20}=x+\dfrac{2}{5}\)
\(\Leftrightarrow\dfrac{x+46}{20}=\dfrac{5x+2}{5}\)
=>100x+40=5x+230
=>95x=190
hay x=2