Câu 1: Thực hiện phép tính a.-19+7+9+19 b, 2/7.5 1/4-2/7.3 1/4 04/09/2021 Bởi Ximena Câu 1: Thực hiện phép tính a.-19+7+9+19 b, 2/7.5 1/4-2/7.3 1/4
Đáp án: `a.-19+7+9+19` `=(-19+19)+7+9` `=16`b, `2/7`.5 `1/4`-`2/7`.3 `1/4` =`2/7`.(5 `1/4`-3 `1/4`) =`2/7`.`2` =`4/7` Bình luận
`a) -19 + 7 + 9 + 19` `= (-19 + 19) + (7 + 9)` `= 0 + 16` `= 16` $\text { b) $\frac{2}{7}$ . 5$\frac{1}{4}$ – $\frac{2}{7}$ . 3$\frac{1}{4}$ }$ $\text { = $\frac{2}{7}$ . ( 5$\frac{1}{4}$ – 3$\frac{1}{4}$ ) }$ $\text { = $\frac{2}{7}$ . [ ( 5 + $\frac{1}{4}$ ) – ( 3 + $\frac{1}{4}$ ) ] }$ $\text { = $\frac{2}{7}$ . ( 5 + $\frac{1}{4}$ – 3 – $\frac{1}{4}$ ) }$ `= 2/7 . ( 5 – 3 )` `= 2/7 . 2` `= 4/7` Bình luận
Đáp án:
`a.-19+7+9+19`
`=(-19+19)+7+9`
`=16`
b, `2/7`.5 `1/4`-`2/7`.3 `1/4`
=`2/7`.(5 `1/4`-3 `1/4`)
=`2/7`.`2`
=`4/7`
`a) -19 + 7 + 9 + 19`
`= (-19 + 19) + (7 + 9)`
`= 0 + 16`
`= 16`
$\text { b) $\frac{2}{7}$ . 5$\frac{1}{4}$ – $\frac{2}{7}$ . 3$\frac{1}{4}$ }$
$\text { = $\frac{2}{7}$ . ( 5$\frac{1}{4}$ – 3$\frac{1}{4}$ ) }$
$\text { = $\frac{2}{7}$ . [ ( 5 + $\frac{1}{4}$ ) – ( 3 + $\frac{1}{4}$ ) ] }$
$\text { = $\frac{2}{7}$ . ( 5 + $\frac{1}{4}$ – 3 – $\frac{1}{4}$ ) }$
`= 2/7 . ( 5 – 3 )`
`= 2/7 . 2`
`= 4/7`