Tìm x:
\(\frac{x+5}{20}+\frac{x+4}{19}=2\)
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a)\(\frac{x}{5}=\frac{25}{30}+\frac{-19}{30}=\frac{6}{30}=\frac{1}{5}\Rightarrow x=1\)
b)\(\frac{9}{x}=\frac{8}{20}+\frac{7}{20}=\frac{15}{20}=\frac{3}{4}=\frac{9}{12}\Rightarrow x=12\)
[ 19/20 x 3/4 + 1/20 x 3/4 ] x [ 1/2 x 3/4 -2/4 x 3/4 ]
=[ 3/4 x [19/20 + 1/20 ] x [3/4 x [2/4 - 1/2]
=[ 3/4 x 1 ] x [3/4 x 0 ]
=0
\(\left(\frac{19}{20}.\frac{3}{4}+\frac{1}{20}.\frac{3}{4}\right).\left(\frac{1}{2}.\frac{3}{4}-\frac{2}{4}.\frac{3}{4}\right)\)
\(=\left(\frac{19}{20}.\frac{3}{4}+\frac{1}{20}.\frac{3}{4}\right).\left(\frac{1}{2}.\frac{3}{4}-\frac{1}{2}.\frac{3}{4}\right)\)
\(=\left(\frac{19}{20}.\frac{3}{4}+\frac{1}{20}.\frac{3}{4}\right).0\)
\(=0\)
\(\frac{x+5}{20}+\frac{x+4}{19}=2\Leftrightarrow\frac{19\left(x+5\right)+20\left(x+4\right)}{380}=2\)
\(\Leftrightarrow\frac{19x+95+20x+80}{380}=2\Leftrightarrow\frac{39x+175}{380}=2\)
\(\Leftrightarrow39x+175=2.380\Leftrightarrow39x+175=760\)
\(\Leftrightarrow39x=585\Leftrightarrow x=15\)
Vậy x = 15
\(\frac{x+5}{20}+\frac{x+4}{19}=2\)
\(\Leftrightarrow\frac{19\left(x+5\right)+20\left(x+4\right)}{380}=2\)
\(\Leftrightarrow19x+95+20x+80=2.380\)
\(\Leftrightarrow39x+175=760\)
\(\Leftrightarrow39x=585\)
\(\Leftrightarrow x=15\)