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\(\frac{19+x}{116-x}=\frac{2}{7}\) ( Đề như này ha ! )
\(7\times\left(19+x\right)=2\times\left(116-x\right)\) (Nhân chéo)
\(7\times19+7\times x=2\times116-2\times x\)
\(7\times x+2\times x=2\times116-7\times19\)
\(9\times x=99\)
\(x=11\)
\(\frac{7}{4}-x\cdot\frac{4}{3}=\frac{5}{19}\)
\(\Rightarrow-x\cdot\frac{4}{3}=\frac{5}{19}-\frac{7}{4}\)
\(\Rightarrow-x\cdot\frac{4}{3}=-\frac{113}{76}\)
\(\Rightarrow x\cdot\frac{4}{3}=\frac{113}{76}\)
\(\Rightarrow x=\frac{113}{76}:\frac{4}{3}=\frac{339}{304}\)
Bài 1:
A = 1996 x 1997 x 1998 x 1999 + 2021 x 2022 x 2023 x 2024
A = (1996 x 1997) x (1998 x 1999) + (2021 x 2022) x (2023 x 2024)
A = \(\overline{..2}\) x \(\overline{..2}\) + \(\overline{..2}\) x \(\overline{..2}\)
A = \(\overline{..4}\) + \(\overline{..4}\)
A = \(\overline{..8}\)
\(\frac{7}{4}-x.\frac{3}{4}=\frac{5}{19}\)
\(\Rightarrow1+\frac{3}{4}-x.\frac{3}{4}=\frac{5}{9}\)
\(\Rightarrow\frac{3}{4}.\left(1-x\right)=\frac{5}{9}-1=-\frac{4}{9}\)
\(\Rightarrow1-x=-\frac{4}{9}:\frac{3}{4}=-\frac{16}{27}\)
\(\Rightarrow x=1-\left(-\frac{16}{27}\right)=1+\frac{16}{27}=1\frac{16}{27}\)
a) 3 x X x 2/3 = 4/5
3.x=6/5
x=2/5
b) 3,94 x 18,24 + 18,24 x 3,72 + 18,24 x 2,34
=18,24(3,94+3,72+2,34)
=18,24.10
=182,4
d) 8/19 x 2/7 + 8/19 x 1/7 + 8/19 x 4/7
=8/19(2/7+1/7+4/7)
=8/19.1
=8/19