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a) x : 2,5 = 1/100
x = 1/250 * 2,5
x= 1/100
b) 5/3= x : 4/5
x= 4/5 * 5/3
x= 4/3
a) \(x\div2.5=0.003\div0.75\)
\(x\div2.5=0.004\)
\(x=0.004×2.5\)
\(x=0.01\)
Vậy, \(x=0.01\)
b) \(\frac{2}{3}\div0.4=x\div\frac{4}{5}\)
\(x\div\frac{4}{5}=\frac{5}{3}\)
\(x=\frac{5}{3}×\frac{4}{5}\)
\(x=\frac{20}{15}=\frac{4}{3}\)
Vậy, \(x=\frac{4}{3}\)
Cbht
a, |0,75 - x| = 2,5
=> 0,75 - x = 2,5 hoặc 0,75 - x = -2,5
=> x = -1,75 hoặc x = 3,25
vậy_
\(|0,75-x|=2,5\)
\(\Rightarrow\hept{\begin{cases}0,75-x=2,5\\0,75-x=-2,5\end{cases}\Rightarrow\hept{\begin{cases}x=-1,75\\x=3,25\end{cases}}}\)
\(a,\left[0,75x+\frac{5}{2}\right]-\frac{4}{7}-\left[-\frac{1}{3}\right]=-\frac{5}{6}\)
\(\Leftrightarrow\left[0,75x+\frac{5}{2}\right]-\frac{4}{7}+\frac{1}{3}=-\frac{5}{6}\)
\(\Leftrightarrow\left[0,75x+\frac{5}{2}\right]=-\frac{5}{6}-\frac{1}{3}+\frac{4}{7}\)
\(\Leftrightarrow0,75x+\frac{5}{2}=-\frac{25}{42}\)
\(\Leftrightarrow0,75x=-\frac{65}{21}\Leftrightarrow x=-\frac{260}{63}\)
\(b,\left[4x-9\right]\left[2,5+-\frac{7}{3}x\right]=0\)
\(\Leftrightarrow\orbr{\begin{cases}4x-9=0\\2,5+-\frac{7}{3}x=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{9}{4}\\x=\frac{15}{14}\end{cases}}\)
Vậy \(x\in\left\{\frac{9}{4};\frac{15}{14}\right\}\)
Tham khảo nhé phamthiminhanh
2,5. 0,75 + 2,5.0,25 - 1,5
=2,5.(0,75 + 0,25) - 1,5
= 2,5.1 - 1,5
= 2,5 - 1,5
= 1
Bài 1: 25/100 = 0,25 ; 1999/1000 = 1,999
b) 0,75 = 75/100; 2,5 = 25/10
Bài 2 :
Ta có :X = 20012001 + 1999 x 20012001
X = 1999 + 1 x 20012001
X = 2000 x 20012001
Ta có :Y = 20012001 x 2001 - 20012001
Y = 20012001 x 2001 - 1
Y = 20012001 x 2000
Ta thấy :2000 x 20012001 = 20012001 x 2000
Vậy : X = Y
`0,75-43/80:(-4/5+2,5*3/4)`
`=0,75-43/80:(-4/5+15/8)`
`=0,75-43/80:43/40`
`=3/4-1/2`
`=1/4`
0,75 - \(\dfrac{43}{80}\) : ( - \(\dfrac{4}{5}\) + 2,5 \(\times\) \(\dfrac{3}{4}\))
= 0,75 - \(\dfrac{43}{80}\) : ( - \(\dfrac{4}{5}\) + \(\dfrac{15}{8}\))
= 0,75 - \(\dfrac{43}{80}\) : \(\dfrac{43}{40}\)
= 0,75 - \(\dfrac{1}{2}\)
= 0,75 - 0,5
= 0,25
\(=\frac{3}{4}-\frac{43}{80}:\left(\frac{-4}{5}+\frac{5}{2}.\frac{3}{4}\right)\)
\(=\frac{3}{4}-\frac{43}{80}:\left(\frac{-4}{5}+\frac{15}{8}\right)\)
\(=\frac{3}{4}-\frac{43}{80}:\frac{43}{40}\)
\(=\frac{4}{3}-\frac{1}{2}=\frac{5}{6}\)
\(A=\dfrac{\dfrac{3}{8}-\dfrac{3}{10}+\dfrac{3}{11}+\dfrac{3}{12}}{-\dfrac{5}{8}+\dfrac{5}{10}-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{\dfrac{3}{2}+\dfrac{3}{3}-\dfrac{3}{4}}{\dfrac{5}{2}+\dfrac{5}{3}-\dfrac{5}{4}}\\ A=\dfrac{3\left(\dfrac{1}{8}-\dfrac{1}{10}+\dfrac{1}{11}+\dfrac{1}{12}\right)}{-5\left(\dfrac{1}{8}-\dfrac{1}{10}+\dfrac{1}{11}+\dfrac{1}{12}\right)}+\dfrac{3\left(\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\right)}{5\left(\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\right)}\\ A=\dfrac{-3}{5}+\dfrac{3}{5}=0\)
\(A=\dfrac{0,375-0,3+\dfrac{3}{11}+\dfrac{3}{12}}{-0,625+0,5-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{1,5+1-0,75}{2,5+\dfrac{5}{3}-1,25}=\dfrac{3\left(0,125-0,1+\dfrac{1}{11}+\dfrac{1}{12}\right)}{-5\left(0,125-0,1+\dfrac{5}{11}+\dfrac{5}{12}\right)}+\dfrac{\dfrac{3}{5}\left(2,5+\dfrac{5}{3}-1,25\right)}{2,5+\dfrac{5}{3}-1,25}=-\dfrac{3}{5}+\dfrac{3}{5}=0\)