Bài 1:
a) \(5\dfrac{5}{47}+\dfrac{37}{53}+2,7-\dfrac{5}{47}+\dfrac{6}{53}\)
= \(5+\dfrac{5}{47}+\dfrac{37}{53}+2,7-\dfrac{5}{47}+\dfrac{6}{53}\)
\(=\left(5+\dfrac{5}{47}-\dfrac{5}{47}\right)+\left(\dfrac{37}{53}+\dfrac{6}{53}\right)+2,7\)
\(=5+1+2,7\)
\(=8,7\)
d) \(2\dfrac{1}{2}+\dfrac{2}{5}:\left(-\dfrac{4}{9}\right)\)
\(=\dfrac{5}{2}+\dfrac{2}{5}.\dfrac{-9}{4}\)
\(=\dfrac{5}{2}+\dfrac{-9}{10}\)
= \(\dfrac{8}{5}\)
c) \(7:\left(-\dfrac{7}{2}\right)^3+\dfrac{1}{25}.\sqrt{25}.\left|-16\right|\)
\(=7:\dfrac{-343}{8}+\dfrac{1}{25}.5.16\)
\(=7.\dfrac{-8}{343}+\dfrac{16}{5}\)
\(=-\dfrac{8}{49}+\dfrac{16}{5}\)
\(=3\dfrac{9}{245}\)
e) \(2^3+3.\left(\dfrac{1}{2}\right)^0+\left[\left(-2\right)^2:\dfrac{1}{2}\right].8\)
\(=8+3+\left[4:\dfrac{1}{2}\right].8\)
= \(11+8.8\)
= 11 + 64
= 75
g) \(-\dfrac{4}{13}.\dfrac{5}{17}+\dfrac{-12}{13}.\dfrac{4}{17}+\dfrac{4}{13}\)
= \(\dfrac{4}{13}.\dfrac{-5}{17}+\dfrac{-12}{13}.\dfrac{4}{17}+\dfrac{4}{13}\)
= \(\dfrac{4}{13}.\left(-\dfrac{5}{17}+1\right)+-\dfrac{12}{13}.\dfrac{4}{17}\)
\(=\dfrac{4}{13}.\dfrac{12}{17}+\dfrac{-12}{13}.\dfrac{4}{17}\)
\(=\dfrac{4.12}{13.17}-\dfrac{12.4}{13.17}\)
=0
Bài 2:
a) \(\left|x-1,5\right|=2\)
\(\Rightarrow\left[{}\begin{matrix}x-1,5=2\\x-1,5=-2\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=3,5\\x=-0,5\end{matrix}\right.\)
b) \(x+\dfrac{1}{3}=\dfrac{2}{5}-\left(-\dfrac{1}{3}\right)\)
\(x+\dfrac{1}{3}=\dfrac{11}{15}\)
\(x=\dfrac{11}{15}-\dfrac{1}{3}\)
\(x=\dfrac{2}{5}\)
e) \(5x+36=64\Rightarrow5x=28\Rightarrow x=5,6\)
m) \(\left|x\right|+\dfrac{1}{5}=2-\left(\dfrac{2}{3}-\dfrac{3}{4}\right)\)
\(\left|x\right|-\dfrac{1}{5}=\dfrac{25}{12}\)
\(\left|x\right|=\dfrac{25}{12}+\dfrac{1}{5}\)
\(\left|x\right|=\dfrac{137}{60}\Rightarrow\left[{}\begin{matrix}x=-\dfrac{137}{60}\\x=\dfrac{137}{60}\end{matrix}\right.\)
l) \(\left|x+\dfrac{4}{5}\right|-\dfrac{3}{5}=\dfrac{6}{5}\)
\(\left|x+\dfrac{4}{5}\right|=\dfrac{9}{5}\)
\(\Rightarrow\left[{}\begin{matrix}x+\dfrac{4}{5}=\dfrac{9}{5}\\x+\dfrac{4}{5}=-\dfrac{9}{5}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{13}{5}\end{matrix}\right.\)
14 Mẹo Vặt Sáng Tạo Dành Cho Học Sinh - YouTube
mẹo thứ 5 nhá, hữu ích lắm.
