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a)
Dãy trên có số số hạng là:
( 20 - 1 ) : 1 + 1 = 20 ( số hạng )
Tổng của dãy trên là:
( 20 + 1 ) x 20 : 2 = 210
Đáp số: 210
b)
Dãy trên có số số hạng là:
( 21 - 1 ) : 2 + 1 = 11 ( số hạng )
Tổng của dãy trên là:
( 21 + 1 ) x 11 : 2 = 121
Đáp số: 121
c) ( 2x - 1 ) x 2 = 13
2x - 1 = \(\dfrac{13}{2}\)
2x = \(\dfrac{15}{2}\)
\(x=\dfrac{15}{4}\)
32 x ( x - 10 ) = 32
( x - 10 ) = 1
x = 11
\(A=1+2+3+...+20\)
Số hạng:
\(\left(20-1\right):1+1=20\) (số hạng)
Tổng: \(\left(20+1\right)\cdot20:2=210\)
\(B=1+3+5+...+21\)
Số hạng:
\(\left(21-1\right):2+1=11\) (số hạng)
Tổng: \(\left(21+1\right)\cdot11:2=121\)
\(\left(2x-1\right)\cdot2=13\)
\(\Rightarrow2x-1=\dfrac{13}{2}\)
\(\Rightarrow2x=\dfrac{15}{2}\)
\(\Rightarrow x=\dfrac{15}{4}\)
\(32\cdot\left(x-10\right)=32\)
\(\Rightarrow x-10=1\)
\(\Rightarrow x=11\)
d) Ta có: \(32\%-0.25:x=-\dfrac{17}{5}\)
\(\Leftrightarrow0.25:x=\dfrac{8}{25}+\dfrac{17}{5}=\dfrac{93}{25}\)
hay \(x=\dfrac{25}{372}\)
Vậy: \(x=\dfrac{25}{372}\)
e) Ta có: \(\left(x+\dfrac{1}{5}\right)^2+\dfrac{17}{25}=\dfrac{26}{25}\)
\(\Leftrightarrow\left(x+\dfrac{1}{5}\right)^2=\dfrac{9}{25}\)
\(\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{5}=\dfrac{3}{5}\\x+\dfrac{1}{5}=-\dfrac{3}{5}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{5}\\x=-\dfrac{4}{5}\end{matrix}\right.\)
Vậy: \(x\in\left\{\dfrac{2}{5};-\dfrac{4}{5}\right\}\)
f) Ta có: \(-\dfrac{32}{27}-\left(3x-\dfrac{7}{9}\right)^3=-\dfrac{24}{27}\)
\(\Leftrightarrow\left(3x-\dfrac{7}{9}\right)^3=\dfrac{-8}{27}\)
\(\Leftrightarrow3x-\dfrac{7}{9}=-\dfrac{2}{3}\)
\(\Leftrightarrow3x=\dfrac{1}{9}\)
hay \(x=\dfrac{1}{27}\)
g) Ta có: \(60\%\cdot x+0.4x+x:3=2\)
\(\Leftrightarrow\dfrac{4}{3}x=2\)
hay \(x=\dfrac{3}{2}\)
Vậy: \(x=\dfrac{3}{2}\)
h) PT \(\Leftrightarrow\left|\dfrac{20}{9}-x\right|=\dfrac{2}{9}\) \(\Rightarrow\left[{}\begin{matrix}\dfrac{20}{9}-x=\dfrac{2}{9}\\x-\dfrac{20}{9}=\dfrac{2}{9}\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=\dfrac{22}{9}\end{matrix}\right.\)
Vậy ...
i) PT \(\Leftrightarrow\dfrac{8}{5}+\dfrac{2}{5}x=\dfrac{16}{5}\) \(\Leftrightarrow\dfrac{2}{5}x=\dfrac{8}{5}\) \(\Leftrightarrow x=4\)
Vậy ...
\(a,[(2\cdot x-11):3+1]\cdot5=20\\\Rightarrow (2x-11):3+1=20:5\\\Rightarrow (2x-11):3+1=4\\\Rightarrow (2x-11):3=4-1\\\Rightarrow (2x-11):3=3\\\Rightarrow2x-11=3\cdot3\\\Rightarrow2x-11=9\\\Rightarrow2x=9+11\\\Rightarrow2x=20\\\Rightarrow x=20:2=10\)
\(b,(25-2x)^3:5-3^2=4^2\\\Rightarrow(25-2x)^3:5-9=16\\\Rightarrow(25-2x)^3:5=16+9\\\Rightarrow(25-2x)^3:5=25\\\Rightarrow(25-2x)^3=25\cdot5\\\Rightarrow(25-2x)^3=125\\\Rightarrow(25-2x)^3=5^3\\\Rightarrow25-2x=5\\\Rightarrow2x=25-5\\\Rightarrow2x=20\\\Rightarrow x=20:2=10\\Toru\)
10 . 58 . 5 + 32 . 2 . 25 + 50 . 10
= 50 . 58 + 50 . 32 + 50 . 10
= 50 . ( 58 + 32 + 10 )
= 50 . 100
= 5000
20 - 2 . ( x - 1 ) = 4
\(\Rightarrow\)2 . ( x - 1 ) = 16
\(\Rightarrow\)x - 1 = 16 : 2
\(\Rightarrow\)x - 1 = 8
\(\Rightarrow\)x = 9
( x + 1 )2 = 9 = 32 = ( -3 )2
\(\Rightarrow\orbr{\begin{cases}x+1=3\\x+1=-3\end{cases}\Rightarrow\orbr{\begin{cases}x=3-1\\x=3+1\end{cases}\Rightarrow}\orbr{\begin{cases}x=2\\x=4\end{cases}}}\)
a) x = 2.
b) x = 7.
c) x= 12.
d) x= 45.
e) x = 18.
f) x = 10.
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hk tốt
mấy bài này dễ
mik trả lời cho bn tham khảo thôi
a) \(\frac{x^7}{3^5}=9\)
=> \(\frac{x^7}{3^5}=3^2\)
=> x7 = 32 . 35 = 37
=> x = 3
b) \(\frac{32}{x^7}=4\)
=> \(\frac{2^5}{x^7}=2^2\)
=> \(2^2\cdot x^7=2^5\)
=> \(x^7=\frac{2^5}{2^2}=2^3\)
=> không tìm được x
2. \(\frac{2^{30}}{3^{20}}-\left(\frac{2}{3}\right)^{20}\cdot2^{10}\)
\(=\frac{2^{30}}{3^{20}}-\frac{2^{20}}{3^{20}}\cdot2^{10}\)
\(=\frac{2^{30}}{3^{20}}-\frac{2^{30}}{3^{20}}=0\)
a, \(x\cdot\dfrac{-5}{8}=\dfrac{15}{32}\)
\(x=\dfrac{15}{32}:\dfrac{-5}{8}\)
\(x=\dfrac{-3}{4}\)
b, \(\dfrac{3}{10}:x=\dfrac{-9}{20}\)
\(x=\dfrac{3}{10}:\dfrac{-9}{20}\)
\(x=-\dfrac{2}{3}\)
c, \(\dfrac{-1}{4}x+\dfrac{4}{5}=\dfrac{3}{4}\)
\(\dfrac{-1}{4}x=\dfrac{3}{4}-\dfrac{4}{5}\)
\(\dfrac{-1}{4}x=-\dfrac{1}{20}\)
\(x=-\dfrac{1}{20}:\dfrac{-1}{4}\)
\(x=\dfrac{1}{5}\)
d, \(\dfrac{-7}{8}+\dfrac{2}{3}:x=\dfrac{3}{5}\cdot\dfrac{-5}{12}\)
\(\dfrac{-7}{8}+\dfrac{2}{3}:x=-\dfrac{1}{4}\)
\(\dfrac{2}{3}:x=-\dfrac{1}{4}+\dfrac{-7}{8}\)
\(\dfrac{2}{3}:x=\dfrac{5}{8}\)
\(x=\dfrac{2}{3}:\dfrac{5}{8}\)
\(x=\dfrac{16}{15}\)
#YVA6
\(a,x.\dfrac{-5}{8}=\dfrac{15}{32}\)
\(\Leftrightarrow x=\dfrac{15}{32}:\dfrac{-5}{8}\)
\(\Leftrightarrow x=\dfrac{15}{32}.\dfrac{-8}{5}\)
\(\Leftrightarrow x=-\dfrac{3}{4}\)
\(b,\dfrac{3}{10}:x=-\dfrac{9}{20}\)
\(\Leftrightarrow x=\dfrac{3}{10}:\dfrac{-9}{20}\)
\(\Leftrightarrow x=\dfrac{3}{10}.\dfrac{-20}{9}\)
\(\Leftrightarrow x=-\dfrac{2}{3}\)
\(c,-\dfrac{1}{4}x+\dfrac{4}{5}=\dfrac{3}{4}\)
\(\Leftrightarrow-\dfrac{1}{4}x=\dfrac{3}{4}-\dfrac{4}{5}\)
\(\Leftrightarrow-\dfrac{1}{4}x=-\dfrac{1}{20}\)
\(\Leftrightarrow x=-\dfrac{1}{20}\times\left(-4\right)\)
\(\Leftrightarrow x=\dfrac{1}{5}\)
\(d,-\dfrac{7}{8}+\dfrac{2}{3}:x=\dfrac{3}{5}.\dfrac{-5}{12}\)
\(\Leftrightarrow-\dfrac{7}{8}+\dfrac{2}{3}:x=-\dfrac{1}{4}\)
\(\Leftrightarrow\dfrac{2}{3}:x=-\dfrac{1}{4}+\dfrac{7}{8}\)
\(\Leftrightarrow\dfrac{2}{3}:x=\dfrac{5}{8}\)
\(\Leftrightarrow x=\dfrac{2}{3}:\dfrac{5}{8}\)
\(\Leftrightarrow x=\dfrac{16}{15}\)
`#3107.101107`
a,
`2x + 3x = 5^7 \div 5^5`
$\Rightarrow (2 + 3)x = 5^{7 - 5}$
$\Rightarrow 5x = 5^2$
$\Rightarrow 5x = 25$
$\Rightarrow x = 25 \div 5$
$\Rightarrow x = 5$
Vậy, `x = 5`
b,
`5(7x - 45) = 2^3 . 5^2 - 3^2 . 20`
`\Rightarrow 5(7x - 45) = 8.25 - 9.20`
`\Rightarrow 5(7x - 45) = 40.5 - 36.5`
`\Rightarrow 5(7x - 45) = 5.(40 - 36)`
`\Rightarrow 5(7x - 45) = 5.4`
`\Rightarrow 7x - 45 = 4`
`\Rightarrow 7x = 49`
`\Rightarrow x = 49 \div 7`
`\Rightarrow x = 7`
Vậy, `x = 7.`
A) (2+3).x=5 mũ 2
5.x=5 mũ 2
5.x=25
x=25:5
x=5
vậy x=5
câu B ko bt làm bn ạ
5.(x+32)+1=20
5.(x+32)=19
x+32=3,8
x=-5,2