Tính hợp lí( Nếu có thể)
a) (-2/5+1/4):(1-2/5)
b) 3/4- 1 và 1/2+0,5:5/12
c) 1/5.4/7+1/5:7/10-1/5
d) (-2)mũ 2-1 và 5/27.( -3/2)mũ 3
Tính hợp lí( Nếu có thể)
a) (-2/5+1/4):(1-2/5)
b) 3/4- 1 và 1/2+0,5:5/12
c) 1/5.4/7+1/5:7/10-1/5
d) (-2)mũ 2-1 và 5/27.( -3/2)mũ 3
`a) (-2/5+1/4):(1-2/5)`
`=(-8/20+5/20):(5/5-2/5)`
`=-3/20 : 3/5`
`=-3/20 . 5/3`
`=-1/4.`
`b) 3/4- 1 1/2+0,5:5/12`
`=3/4-3/2+1/2. 12/5`
`=15/20 – 30/20 + 6/5`
`=15/20 – 30/20 + 24/20`
`=9/20.`
`c)1/5. 4/7+1/5:7/10-1/5`
`=1/5. 4/7+1/5. 10/7-1/5`
`=1/5.(4/7+10/7-1)`
`=1/5. (14/7 – 1)`
`=1/5. (2 – 1)`
`=1/5 . 1`
`=1/5.`
`d) (-2)^2-1 5/27.( -3/2)^3`
`=4 – 32/27. (-27/8)`
`= 4- (-4)`
`=4+4`
`=8.`
Đáp án:
a) `(“\frac{-2}{5}` + `\frac{1}{4}` `)` : `(“1` -`\frac{2}{5}“)`
= `\frac{-3}{20}` : `\frac{3}{5}`
= `\frac{-3}{20}` . `\frac{5}{3}`
= `\frac{-1}{4}`
b) `\frac{3}{4}` – `1“\frac{1}{2}` + `0,5` : `\frac{5}{12}`
= `\frac{3}{4}` – `\frac{3}{2}` + `\frac{1}{2}` : `\frac{5}{12}`
= `\frac{3}{4}` – `\frac{3}{2}` + `\frac{6}{5}`
= `\frac{15}{20}` – `\frac{30}{20}` + `\frac{24}{20}`
= `\frac{9}{20}`
c) `\frac{1}{5}` . `\frac{4}{7}` + `\frac{1}{5}` : `\frac{7}{10}` – `\frac{1}{5}`
= `\frac{1}{5}` . `\frac{4}{7}` + `\frac{1}{5}` . `\frac{10}{7}` – `\frac{1}{5}`
= `\frac{1}{5}` . `\frac{4}{7}` + `\frac{1}{5}` . `\frac{10}{7}` – `\frac{1}{5}` . `1`
= `\frac{1}{5}` . `(“\frac{4}{7}` + `\frac{10}{7}` – `1“)`
= `\frac{1}{5}` . `1`
= `\frac{1}{5}`
c) $(-2)^{2}$ – `1“\frac{5}{27}` . `(“\frac{-3}{2}^{3}“)`
= `4` – `\frac{32}{27}` . `(“\frac{-27}{8}“)`
= `4` – `(“-4“)`
= `4` + `4`
= `8`