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a) \(\frac{2}{5}+\left(\frac{3}{4}-\frac{7}{10}\right)\)
\(=\frac{2}{5}+\frac{1}{20}\)
\(=\frac{9}{20}\)
b) \(\frac{-1}{8}-\left(\frac{2}{3}-\frac{11}{12}\right)\)
\(=-\frac{1}{8}-\left(-\frac{1}{4}\right)\)
\(=\frac{1}{8}\)
c) \(\frac{7}{5}-\left(\frac{1}{6}+\frac{9}{10}\right)\)
\(=\frac{7}{5}-\frac{16}{15}\)
\(=\frac{1}{3}\)
d) \(\frac{2}{3}+\left(-\frac{1}{4}\right)+\frac{7}{12}-\left(-\frac{1}{4}\right)-\frac{5}{6}\)
\(=\left(\frac{2}{3}+\frac{7}{12}-\frac{5}{6}\right)+\left(-\frac{1}{4}+\frac{1}{4}\right)\)
\(=\left(\frac{5}{4}-\frac{5}{6}\right)+0\)
\(=\frac{5}{12}\)
e) \(2-\left\{\frac{1}{2}-\left[2-\left(\frac{1}{2}+2\right)-\frac{1}{2}\right]+2\right\}\)
\(=2-\left[\frac{1}{2}-\left(2-\frac{5}{2}-\frac{1}{2}\right)+2\right]\)
\(=2-\left[\frac{1}{2}-\left(-1\right)+2\right]\)
\(=2-\frac{7}{2}\)
\(=-\frac{3}{2}\)
Bài 2:
b: x+25%x=-1,25
=>1,25x=-1,25
hay x=-1
c: x-75%x=1/4
=>1/4x=1/4
hay x=1
Bài 2:
a: =3/2-11/4=6/4-11/4=-5/4
b: =-49/6-17/2=-49/6-51/6=-100/6=-50/3
a
\(5\frac{4}{7}:x+=13\)
\(\frac{39}{7}:x=13\)
\(x=\frac{39}{7}:13\)
\(x=\frac{3}{7}\)
\(\frac{4}{7}x=\frac{9}{8}-0,125\)
\(\frac{4}{7}x=1\)
\(x=1:\frac{4}{7}\)
\(x=\frac{7}{4}=1\frac{3}{4}\)
Tìm x :
a) \(2.x.\frac{-3}{4}=-\frac{5}{12}\)
\(\Rightarrow2x=-\frac{5}{12}:-\frac{3}{4}\)
\(\Rightarrow2x=\frac{5}{9}\)
\(\Rightarrow x=\frac{5}{9}:2\)
\(\Rightarrow x=\frac{5}{18}\)
Vậy : \(x=\frac{5}{18}\)
b) \(\frac{2}{3}+\frac{1}{3}.x=7\)
\(\Rightarrow\frac{1}{3}.x=7-\frac{2}{3}\)
\(\Rightarrow\frac{1}{3}.x=\frac{19}{3}\)
\(\Rightarrow x=\frac{19}{3}:\frac{1}{3}\)
\(\Rightarrow x=19\)
Vậy : \(x=19\)
c) \(\left(4.x+\frac{1}{8}\right)=\frac{3}{10}\)
\(\Rightarrow4.x=\frac{3}{10}-\frac{1}{8}\)
\(\Rightarrow4.x=\frac{7}{40}\)
\(\Rightarrow x=\frac{7}{40}:4\)
\(\Rightarrow x=\frac{7}{160}\)
Vậy : \(x=\frac{7}{160}\)
d) \(\frac{1}{3}.x-5=1\frac{1}{2}\)
\(\Rightarrow\frac{1}{3}.x-5=\frac{3}{2}\)
\(\Rightarrow\frac{1}{3}.x=\frac{3}{2}+5\)
\(\Rightarrow\frac{1}{3}.x=\frac{13}{2}\)
\(\Rightarrow x=\frac{13}{2}:\frac{1}{3}\)
\(\Rightarrow x=\frac{39}{2}\)
Vậy : \(x=\frac{39}{2}\)
e) \(-\frac{2}{3}.x+\frac{1}{3}=-\frac{1}{2}\)
\(\Rightarrow-\frac{2}{3}.x=-\frac{1}{2}-\frac{1}{3}\)
\(\Rightarrow-\frac{2}{3}.x=-\frac{5}{6}\)
\(\Rightarrow x=-\frac{5}{6}:\left(-\frac{2}{3}\right)\)
\(\Rightarrow x=\frac{5}{4}\)
Vậy : \(x=\frac{5}{4}\)
Thực hiện phép tính
a ) \(\frac{2}{5}+\frac{-1}{6}-\frac{3}{4}-\frac{-2}{3}\)
= \(\frac{2}{5}+\frac{-1}{6}+\frac{-3}{4}+\frac{2}{3}\)
= \(\left(\frac{2}{5}+\frac{-3}{4}\right)+\left(\frac{-1}{6}+\frac{2}{3}\right)\)
= \(\left(\frac{8}{20}+\frac{-15}{20}\right)+\left(\frac{-1}{6}+\frac{4}{6}\right)\)
= \(\left(\frac{8+\left(-15\right)}{20}\right)+\left(\frac{\left(-1\right)+4}{6}\right)\)
= \(\frac{-7}{20}+\frac{1}{2}\)
= \(\frac{-7}{20}+\frac{10}{20}=\frac{\left(7\right)+10}{20}=\frac{3}{20}\)
tk mk nha
đang âm rất nhiều rồi , giúp nha !!!!!
D=1/2-1/24 +1/27-1/210 +.......+1/258
2D =1 - 1/2-1/24 +1/27-1/210 +.......+1/257
2D -D =(1 - 1/2-1/24 +1/27-1/210 +.......+1/257)-(1/2-1/24 +1/27-1/210 +.......+1/258)
D=1-1/258