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a:=>0,75x-x+1,25x=0,2
=>x=0,2
b: =>1/3-x=-3/6+4/6=1/6
=>x=1/3-1/6=1/6
c: =>(x-1)/45=-6/30=-1/5
=>x-1=-9
=>x=-8
d: =>(2/5x-1)=-5/7
=>2/5x=2/7
=>x=5/7
e: =>2/7-x=2/5
=>7-x=5
=>x=2
f: =>2x+3/3=10/3
=>2x+3=10
=>2x=7
=>x=7/2
g: =>(14+x)/7=15/7
=>x+14=15
=>x=1
h: =>(2x+3)/x=13/x
=>2x+3=13
=>2x=10
=>x=5
\(-45\%x+2\dfrac{3}{8}=-1\dfrac{31}{40}\)
\(\Rightarrow-\dfrac{9}{20}x+\dfrac{19}{8}=-\dfrac{71}{40}\)
\(\Rightarrow-\dfrac{9}{20}x=-\dfrac{71}{40}-\dfrac{19}{8}\)
\(\Rightarrow-\dfrac{9}{20}x=-\dfrac{83}{20}\)
\(\Rightarrow x=-\dfrac{83}{20}:\left(-\dfrac{9}{20}\right)\)
\(\Rightarrow x=\dfrac{83}{9}\)
Vậy \(x=\dfrac{83}{9}\)
\(-45\%x+2\dfrac{3}{8}=-1\dfrac{31}{40}\)
\(\Leftrightarrow\dfrac{9}{20}x+\dfrac{19}{8}=-\dfrac{71}{40}\)
\(\Leftrightarrow\dfrac{9}{20}x=-\dfrac{71}{40}-\dfrac{19}{8}\)
\(\Leftrightarrow\dfrac{9}{20}x=-\dfrac{83}{20}\)
\(\Leftrightarrow x=-\dfrac{83}{20}:\dfrac{9}{20}\)
\(\Leftrightarrow x=-\dfrac{83}{20}.\dfrac{20}{9}\)
\(\Leftrightarrow x=-\dfrac{83}{9}\)
\(-\dfrac{x}{27}-1=\dfrac{2}{3}\)
\(\Rightarrow-\dfrac{x}{27}=\dfrac{2}{3}+1=\dfrac{5}{3}\)
\(\Rightarrow-3x=27.5\)
\(\Rightarrow x=-135:\left(-3\right)\)
\(\Rightarrow x=-45\)
`->B`
Lời giải:
Gọi tổng trong ngoặc là $A$
$2A=\frac{3-1}{1.2.3}+\frac{4-2}{2.3.4}+....+\frac{10-8}{8.9.10}$
$=\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+...+\frac{1}{8.9}-\frac{1}{9.10}$
$=\frac{1}{1.2}-\frac{1}{9.10}=\frac{1}{2}-\frac{1}{90}=\frac{22}{45}$
Vậy $\frac{22}{45}x=\frac{23}{45}$
$\Rightarrow x=\frac{23}{45}: \frac{22}{45}=\frac{23}{22}$
$x$ ở cuối là sao đây bạn? Nhân riêng với $\frac{1}{8.9.10}$ à?
\(\dfrac{1}{7}=\dfrac{8}{-x}\)=> \(-x=56\)
=> \(x=56\)
2) => 18x = 18
=> x = 1
3) \(\dfrac{-4}{3}+x=\dfrac{-11}{6}\)
=> \(x=\dfrac{-11}{6}+\dfrac{4}{3}\)
=> \(x=\dfrac{-1}{2}\)
4) 45%.x =\(\dfrac{3}{5}\)
=> \(x=\dfrac{3}{5}:\dfrac{9}{20}\)
=> \(x=\dfrac{4}{3}\)
\(\left(\dfrac{1}{1.2.3}+\dfrac{1}{2.3.4}+...+\dfrac{1}{8.9.10}\right).x=\dfrac{22}{45}\)
=> \(\dfrac{1}{2}.\left(\dfrac{2}{1.2.3}+\dfrac{2}{2.3.4}+...+\dfrac{2}{8.9.10}\right).x=\dfrac{22}{45}\)
=> \(\dfrac{1}{2}.\left(\dfrac{1}{1.2}-\dfrac{1}{2.3}+\dfrac{1}{2.3}-...-\dfrac{1}{9.10}\right).x=\dfrac{22}{45}\)
=> \(\dfrac{1}{2}.\left(\dfrac{1}{1.2}-\dfrac{1}{9.10}\right).x=\dfrac{22}{45}\)
=> \(\dfrac{1}{2}.\dfrac{22}{45}.x=\dfrac{22}{45}\)
=> \(\dfrac{1}{2}.x=1\)
=> \(x=2\)
Vậy x = 2
Chúc bạn học tốt !!!
2000000000-1000000000
x=30 (chắc thế)