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Bài làm :
\(a,23+x:2=37\)
\(x:2=14\)
\(x=14\times2\)
\(x=28\)
\(b,x-320:32=4\times16\)
\(x-10=64\)
\(x=64+10\)
\(x=74\)
\(c,3x-2018:2=23\)
\(3x-1009=23\)
\(3x=23+1009\)
\(3x=1032\)
\(x=344\)
\(d,\left(9x-21\right):3=2\)
\(9x-21=6\)
\(9x=6+21\)
\(9x=27\)
\(x=3\)
\(e,15:x+120:12=15\)
\(15:x+10=15\)
\(15:x=15-10\)
\(15:x=5\)
\(x=3\)
Học tốt nhé
a ) 10 x X - 1 - 3 - 5 - 7 - ... - 19 = 2 + 4 + 6 + ... + 20
10 x X - 1 - 3 - 5 - 7 - ... - 19 = 110
10 x X - ( 1 + 3 + 5 + 7 + ... + 19 ) = 110
10 x X - 100 = 110
10 x X = 110 + 100
10 x X = 210
X = 210 : 10
X = 21
a) x= \(\frac{-5}{12}\)
b) x = \(\frac{2}{5}\)
c) x =\(\frac{-87}{140}\)
d) x = \(\frac{109}{140}\)
e) x = \(\frac{13}{63}\)
\(\left(3x-7\right)^3=2^3.3^2+53\)
\(\left(3x-7\right)^3=8.9+53=125\)
\(\Leftrightarrow\left(3x-7\right)^3=125=5^3\)
\(\Leftrightarrow3x-7=5\)
\(\Leftrightarrow3x=5+7\)
\(\Leftrightarrow3x=12\)
\(\Leftrightarrow x=12:3\)
\(\Leftrightarrow x=4\)
g) x - [ 42 + (-28)] = -8
\(\Rightarrow x-\left(42-28\right)=-8\)
\(\Rightarrow x-14=-8\)
\(\Rightarrow x=-8+14\)
\(\Rightarrow x=6\)
e) | x - 3| = |5| + | -7|
\(\Rightarrow\left|x-3\right|=5+7\)
\(\Rightarrow\left|x-3\right|=12\)
\(\Rightarrow\orbr{\begin{cases}x-3=12\\x-3=-12\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=15\\x=-9\end{cases}}\)
`@` `\text {Ans}`
`\downarrow`
`A = 3 + 3^2 + ... + 3^99 + 3^100`
`=> 3A = 3^2 + 3^3 + ... + 3^100 + 3^101`
`=> 3A - A = (3^2 + 3^3 + ... + 3^100 + 3^101) - (3 + 3^2 + ... + 3^99 + 3^100)`
`=> 2A = 3^101 - 3`
`=> 2A + 3 = 3^101 + 3 - 3`
`=> 2A + 3 = 3^101`
Ta có:
`2A + 3 = 3^x`
`=> x = 101.`
A=3+3^2+...+3^100
=>3*A=3^2+3^3+...+3^101
=>2A=3^101-3
=>2A+3=3^101
Theo đề, ta có: 3^x=3^101
=>x=101
3x.12x+3x.(-4)-9x.4x-9x.(-3)=30
36x2-12x-36x2-27x=30
24x-9x=30
15x=30
=>x=30:15
=>x=2