x + 15% x = 1,09 - 0,29 . 1 1/4 / ( 18,9 - 16 13/20 ) .8/9
1 1/4 ; 16 13/20 là hổn
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\(x+15\%x=\left[\left(1,09-0,29\right).1\frac{1}{4}\right]:\left[\left(18,9-16\frac{13}{20}\right).\frac{8}{9}\right]\)
\(x+15\%x=\left[0,8.1\frac{1}{4}\right]:\left[2,25.\frac{8}{9}\right]\)
\(x+15\%x=1:2\)
\(x+15\%x=\frac{1}{2}\)
\(x+15x=\frac{1}{2}\)
\(16x=\frac{1}{2}\)
\(x=\frac{1}{2}:16=\frac{1}{32}\)
Vậy x=1/32
\(B=\frac{\left(1,09-0,29\right).1\frac{1}{4}}{\left(18,9-16\frac{13}{20}\right).\frac{8}{9}}=\frac{0,8.\frac{5}{4}}{\left[\left(18+0,9\right)-\left(16+\frac{13}{20}\right)\right].\frac{8}{9}}\)
\(B=\frac{\frac{4}{5}.\frac{5}{4}}{\left(18+\frac{9}{10}-16-\frac{13}{20}\right).\frac{8}{9}}\)
\(B=\frac{1}{\left[\left(18-16\right)+\left(\frac{9}{10}-\frac{13}{20}\right)\right].\frac{8}{9}}\)
\(B=\frac{1}{\left(2+\frac{1}{4}\right).\frac{8}{9}}\)
\(B=\frac{1}{\frac{9}{4}.\frac{8}{9}}=\frac{1}{2}\)
Bài 4:
b: Ta có: \(2x\left(x-\dfrac{1}{4}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{4}\end{matrix}\right.\)
\(\frac{\left(1,09-0,29\right)x\frac{5}{4}}{\left(18,9-16,65\right)x\frac{8}{9}}\)=\(\frac{\frac{4}{5}x\frac{5}{4}}{\frac{9}{4}x\frac{8}{9}}\)=\(\frac{1}{2}\)\(=0,5\)
\(A=\left[\dfrac{4}{5}\cdot7+\dfrac{16}{25}\right]\cdot\left(7.75\right)-47.86\)
\(=\dfrac{156}{25}\cdot\dfrac{31}{4}-\dfrac{2793}{50}=\dfrac{-15}{2}\)
\(C=\left(0.8\right)\cdot\dfrac{5}{4}:\dfrac{9}{4}\cdot\dfrac{8}{9}=1\cdot\dfrac{4}{9}\cdot\dfrac{8}{9}=\dfrac{32}{81}\)