A= 0.75 *1 3/1+0.01*2.5*40
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a: \(\Leftrightarrow2x=\dfrac{19}{5}:\dfrac{3}{32}=\dfrac{608}{15}\)
hay x=304/15
b: \(\Leftrightarrow0.25x=20\)
hay x=80
c: \(\Leftrightarrow x=\dfrac{1}{100}:\dfrac{5}{2}=\dfrac{2}{500}=\dfrac{1}{250}\)
d: \(\Leftrightarrow0.1x=\dfrac{2}{3}:\dfrac{5}{3}=\dfrac{2}{5}\)
hay \(x=\dfrac{2}{5}:\dfrac{1}{10}=\dfrac{20}{5}=4\)
Bài 1 :
Áp dụng t.c tỉ lệ thức là làm dc thôi bn
Bài 2 :
Đặt :
\(\dfrac{x}{4}=\dfrac{y}{7}=k\)\(\Leftrightarrow\left\{{}\begin{matrix}x=4k\\y=7k\end{matrix}\right.\)\(\left(1\right)\)
Thay \(xy=112\) vào \(\left(1\right)\) ta có :
\(4k.7k=112\)
\(\Leftrightarrow28k^2=112\)
\(\Leftrightarrow k^2=4\)
\(\Leftrightarrow\left[{}\begin{matrix}k^2=2^2\\k^2=\left(-2\right)^2\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}k=2\\k=-2\end{matrix}\right.\)
+) \(k=2\)\(\Leftrightarrow\left\{{}\begin{matrix}x=4.2=8\\y=7.2=14\end{matrix}\right.\)
+) \(k=-2\)\(\Leftrightarrow\left\{{}\begin{matrix}x=4.\left(-2\right)=-8\\y=7.\left(-2\right)=-14\end{matrix}\right.\)
Vậy ..
( x - 1,75 ) : 0,01 /20 = 1025
( x - 1,75 ) : 0,01 = 20500
x - 1,75 = 205
x = 206,75
\(\dfrac{0,375-0,3+\dfrac{3}{11}+\dfrac{3}{12}}{-0,53+0,5-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{1,5+1-0,75}{2,5+\dfrac{5}{3}-1,25}.\)
\(=\dfrac{\dfrac{3}{8}-\dfrac{3}{10}+\dfrac{3}{11}+\dfrac{3}{12}}{-\dfrac{53}{100}+\dfrac{1}{2}-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{\dfrac{3}{2}+1-\dfrac{3}{4}}{\dfrac{5}{2}+\dfrac{5}{3}-\dfrac{5}{4}}.\)
\(=\dfrac{\dfrac{263}{440}}{\dfrac{-1487}{1650}}+\dfrac{\dfrac{7}{4}}{\dfrac{35}{12}}=\dfrac{-3945}{5948}+\dfrac{3}{5}=\dfrac{-1881}{29740}.\)
A = 0.75 * 1 3/1 + 0.01 * 2.5 * 40
A = 0.75 * 4 + 0.01 * 2.5 * 40
A = 3 + 0.01 * 2.5 * 40
A = 3 + 0.025 * 40
A = 3 + 1
A = 4
Tk mk mk tk lại