Đáp án + Giải thích các bước giải:
Bài `1` :
`a,\frac{4}{5}-(-\frac{2}{5})-\frac{7}{10}`
`=\frac{4}{5}+\frac{2}{5}-\frac{7}{10}`
`=\frac{8}{10}+\frac{4}{10}-\frac{7}{10}`
`=\frac{5}{10}`
`=\frac{1}{2}`
`b,3,5:(-1\frac{2}{5})+(-\frac{3}{2})^2 `
`=3,5:(-\frac{7}{5})+\frac{9}{4}`
`=-\frac{5}{2}+\frac{9}{4}`
`=-\frac{10}{4}+\frac{9}{4}`
`=-\frac{1}{4}`
`c,\sqrt{0,01}-\sqrt{0,25}`
`=\frac{1}{10}-\frac{1}{2}`
`=\frac{1}{10}-\frac{5}{10}`
`=-\frac{4}{10}`
`=-\frac{2}{5}`
`------`
Bài `2` :
`a,x:\frac{2}{3}=(\frac{2}{3})^2`
`→x=(\frac{2}{3})^2.\frac{2}{3}`
`→x=(\frac{2}{3})^3`
`→x=\frac{8}{27}`
`b,26x+(1,5)^{3}.8=1`
`→26x+\frac{27}{8}.8=1`
`→26x+27=1`
`→26x=-26`
`->x=-1`
`c,(-\frac{2}{5})^{2}.x=(-\frac{2}{5})^4`
`->x=(-\frac{2}{5})^4:(-\frac{2}{5})^{2}`
`->x=(-\frac{2}{5})^2`
`->x=\frac{4}{25}`
