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mink bit ket qua va cach giai nhung co giao noi giai theo cach do la sai
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a) 2 + 4 + 6 + ... + x = 240
số số hạng : ( x - 2 ) : 2 + 1 = x : 2 ( số )
tổng : ( x + 2 ) . x : 2 = 240
( x + 2 ) . x = 240 x 2
( x + 2 ) . x = 480
Mà .... ( đề sai )
b) 1 + 2 + 3 + ... + x = 306
số số hạng : ( x - 1 ) : 1 + 1 = x ( số )
tổng : ( x + 1 ) . x : 2 = 306
( x + 1 ) . x = 306 . 2
( x + 1 ) . x = 612
Mà .... ( đề sai )
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ta có:x/2+3x/4+x/2+x/4=8
=>(x/2+x/2)+(3x/4+x/4)=8
=>x+x=8
=>2x=8
=>x=4
kích mình nhé
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Ta có (7+x)/12=2/3
suy ra 3(7+x)=24
suy ra 7+x=8
x=1
Ta có (25-x)/18=1/2
suy ra 2(25-x)=18
suy ra 25-x=9
x=16
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\(\frac{5}{3}-\frac{1}{3}:\left(1-x\cdot\frac{1}{3}\right)=\frac{7}{6}\)
=> \(\frac{1}{3}:\left(1-x\cdot\frac{1}{3}\right)=\frac{5}{3}-\frac{7}{6}\)
=> \(\frac{1}{3}:\left(1-x\cdot\frac{1}{3}\right)=\frac{1}{2}\)
=> \(\left(1-x\cdot\frac{1}{3}\right)=\frac{1}{3}:\frac{1}{2}=\frac{1}{3}\cdot2=\frac{2}{3}\)
=> \(1-\frac{x}{3}=\frac{2}{3}\)
=> \(\frac{x}{3}=1-\frac{2}{3}=\frac{1}{3}\)
=> x = 1
\(3-\left(x:\frac{1}{2}+\frac{3}{2}\right)-\frac{1}{4}=\frac{1}{2}\)
=> \(3-\left(x:\frac{1}{2}+\frac{3}{2}\right)=\frac{1}{2}+\frac{1}{4}=\frac{3}{4}\)
=> \(x:\frac{1}{2}+\frac{3}{2}=3-\frac{3}{4}=\frac{9}{4}\)
=> \(x:\frac{1}{2}=\frac{9}{4}-\frac{3}{2}\)
=> \(x:\frac{1}{2}=\frac{3}{4}\)
=> \(x=\frac{3}{4}\cdot\frac{1}{2}=\frac{3}{8}\)
\(\frac{5}{3}-\frac{1}{3}:\left(1-x\times\frac{1}{3}\right)=\frac{7}{6}\)
\(\frac{1}{3}:\left(1-x\times\frac{1}{3}\right)=\frac{5}{3}-\frac{7}{6}\)
\(\frac{1}{3}:\left(1-x\times\frac{1}{3}\right)=\frac{1}{2}\)
\(1-x\times\frac{1}{3}=\frac{1}{3}:\frac{1}{2}\)
\(1-x\times\frac{1}{3}=\frac{2}{3}\)
\(x\times\frac{1}{3}=1-\frac{2}{3}\)
\(x\times\frac{1}{3}=\frac{1}{3}\)
\(x=\frac{1}{3}:\frac{1}{3}\)
\(x=1\)
\(3-\left(x:\frac{1}{2}+\frac{3}{2}\right)-\frac{1}{4}=\frac{1}{2}\)
\(3-\left(x:\frac{1}{2}+\frac{3}{2}\right)=\frac{1}{2}+\frac{1}{4}\)
\(3-\left(x:\frac{1}{2}+\frac{3}{2}\right)=\frac{3}{4}\)
\(x:\frac{1}{2}+\frac{3}{2}=3-\frac{3}{4}\)
\(x:\frac{1}{2}+\frac{3}{2}=\frac{9}{4}\)
\(x:\frac{1}{2}=\frac{9}{4}-\frac{3}{2}\)
\(x:\frac{1}{2}=\frac{3}{4}\)
\(x=\frac{3}{4}\times\frac{1}{2}\)
\(x=\frac{3}{8}\)