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a) \(1+2+3+...+x=325\)
\(\dfrac{x\times\left(x+1\right)}{2}=325\)
\(x\times\left(x+1\right)=325\times2\)
\(x\times\left(x+1\right)=650\)
\(x\times\left(x+1\right)=25\times26\)
\(x=25\)
b) Bạn xem lại đề:
\(a,\frac{1}{2}x+\frac{3}{5}\left(x-2\right)=3\)
\(\Rightarrow\frac{1}{2}x+\frac{3}{5}x-\frac{6}{5}=3\)
\(\Rightarrow x\left(\frac{1}{2}+\frac{3}{5}\right)=3+\frac{6}{5}\)
\(\Rightarrow\frac{11}{10}x=\frac{21}{5}\)
\(\Rightarrow x=\frac{21}{5}:\frac{11}{10}\)
\(\Rightarrow x=\frac{42}{11}\)
\(b,\left(3\frac{1}{2}-x\right).1\frac{1}{4}=-1\frac{1}{20}\)
\(\Rightarrow\left(\frac{7}{2}-x\right)\cdot\frac{5}{4}=-\frac{21}{20}\)
\(\Rightarrow\frac{7}{2}-x=-\frac{21}{20}:\frac{5}{4}\)
\(\Rightarrow\frac{7}{2}-x=-\frac{21}{25}\)
\(\Rightarrow x=\frac{7}{2}--\frac{21}{25}\)
\(\Rightarrow x=\frac{7}{2}+\frac{21}{25}\)
\(\Rightarrow x=\frac{217}{50}\)
Ta có (x+1/2)*(2/3-2x)=0
x+\(\frac{1}{2}\) =0 hoặc \(\frac{2}{3}\) -2x=0
x =0-\(\frac{1}{2}\) 2x = \(\frac{2}{3}\)
x =\(-\frac{1}{2}\) x = \(\frac{2}{3}\) : 2 =\(\frac{1}{3}\)
Vậy x =\(-\frac{1}{2}\)hoặc x = \(\frac{1}{3}\)
Lời giải:
a.
$x=\frac{-5}{6}-\frac{2}{3}=\frac{-3}{2}$
b.
$\frac{2}{3}x=\frac{1}{10}-\frac{1}{2}=\frac{-2}{5}$
$x=\frac{-2}{5}: \frac{2}{3}=\frac{-3}{5}$
c.
$\frac{7}{8}x=\frac{2}{9}-\frac{1}{3}=\frac{-1}{9}$
$x=\frac{-1}{9}: \frac{7}{8}=\frac{-8}{63}$
d.
$\frac{5}{7}: x=\frac{1}{6}-\frac{4}{5}=\frac{-19}{30}$
$x=\frac{5}{7}: \frac{-19}{30}=\frac{-150}{133}$
e.
$(\frac{2}{5}-1\frac{2}{3}):x=\frac{2}{5}+\frac{3}{5}=1$
$\frac{-19}{15}: x=1$
$x=\frac{-19}{15}:1 =\frac{-19}{15}$
f.
$(-\frac{3}{4}+x).2\frac{2}{3}=1$
$\frac{-3}{4}+x=1: 2\frac{2}{3}=\frac{3}{8}$
$x=\frac{3}{8}+\frac{3}{4}=\frac{9}{8}$
Ta có : \(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+1000\right)=5750\)
\(\Leftrightarrow1000x+\left(1+2+...+1000\right)=5750\)
\(\Leftrightarrow1000x+\frac{1001.1000}{2}=5750\)
\(\Leftrightarrow1000x=\frac{5750}{500500}=\frac{23}{2002}\)
\(\Leftrightarrow x=\frac{23}{2002000}\)
(x+1)+(x+2)+...+(x+1000)=5750
=>x.1000+(1+2+3+...+1000)=5750
=>x.1000+[(1000+1).1000:2]=5750
=>1000x+(1001000:2)=5750
=>1000x+500500=5750
=>1000x=5750-500500=-494750
=>x=-494750:1000=-494,75
Có lẽ đúng >: ko chắc :P
câu a+b dùng quy tắc chuyển vế
c, 3.(1/2-x)-5.(x-1/10)=-7/4
=>(3.1/2-3x)-(5x-5.1/10)=-7/4
=>3/2-3x-5x+1/2=-7/4
=>(3/2+1/2)-(3x+5x)=-7/4
=> 2-8x=-7/4
=>8x=15/4
=>x=15/4:8
=>x=15/32
a) 2.(1/4 - 3x) = 1/5 - 4x
=> 1/2 - 6x = 1/5 -4x
=> -6x + 4x = 1/5 - 1/2
=> -2x = -3/10 = 3/20
b) 4.(1/3 - x) + 1/2 = 5/6 +x
=> 4/3 - 4x + 1/2 = 5/6 +x
=> -4x - x = 5/6 - 4/3 - 1/2
=> -5x = -1
=> x= 1/5
c) 3. (1/2 - x) -5. ( x - 1/10) = -7/4
=> 3/2 - 3x - 5x + 1/2 = -7/4
=> -3x - 5x = -7/4 - 3/2 - 1/2
=> -8x = -15/4
=> x = 15/32
a/ \(\left(1.5-3x\right)-3=9\)
\(\Leftrightarrow5-3x=12\)
\(\Leftrightarrow3x=-7\)
\(\Leftrightarrow x=-\frac{7}{3}\)
b/ \(3\left(x+1\right):2=3\)
\(\Leftrightarrow3\left(x+1\right)=6\)
\(\Leftrightarrow x+1=2\)
\(\Leftrightarrow x=1\)
\(\left(1.5-3x\right)-3=9\)
\(\left(5-3x\right)-3=9\)
\(2-3x=9\)
\(-3x=9-2\)
\(x=\frac{-7}{3}\)
\(3.\left(x+1\right):2=3\)
\(\left(3x+3\right):2=3\)
\(3x+3=6\)
\(3x=3\)
\(x=1\)