Bài 1:
a) `(\frac{-2}{3}+\frac{3}{7}): \frac{4}{5}+(\frac{-1}{3}+\frac{4}{7}): \frac{4}{5}`
`= (\frac{-2}{3}+\frac{3}{7}+\frac{-1}{3}+\frac{4}{7}): \frac{4}{5}`
`= [(\frac{-2}{3}+\frac{-1}{3})+(\frac{3}{7}+\frac{4}{7})]: \frac{4}{5}`
`= [(-1)+1]: \frac{4}{5}`
`= 0: \frac{4}{5}`
`= 0`.
b) `sqrt{0,01}. 5- sqrt{0,25}. 4`
`= 0,1. 5- 0,5. 4`
`= 0,5- 2`
`= -1,5`.
Bài 2:
a) `\frac{3x}{10}=\frac{6}{-15}`
`=> \frac{3x}{10}=\frac{-2}{5}`
`=> 3x. 5=-2. 10`
`=> 3x.5=-20`
`=> 3x=-20: 5`
`=> 3x=-4`
`=> x=-4: 3`
`=> x=\frac{-4}{3}`.
Vậy `x=\frac{-4}{3}`.
b) `\frac{2}{3}+\frac{1}{3}: x=\frac{3}{5}`
`1/3: x=3/5- 2/3`
`1/3: x=\frac{-1}{15}`
`x=1/3: \frac{-1}{15}`
`x=1/3. (-15)`
`x=\frac{-1}{45}`.
Vậy `x=\frac{-1}{45}`.
c) `|x-0,25|. 5/6= 1 2/3`
`|x-0,25|. 5/6=5/3`
`|x-0,25|=5/3: 5/6`
`|x-0,25|=5/3. 6/5`
`|x-0,25|=2`
`=> x-0,25=2` hoặc `x-0,25=-2`
+) `x-0,25=2`
`x=2+0,25`
`x=2,25`.
+) `x-0,25=-2`
`x=-2+0,25`
`x=-1,75`.
Vậy `x∈{-1,75; 2,25}`.
