Tính hợp lí a, 25.(-1/5)2 – 3/5 b, (-2/7:6/14) x 8 c, |-2,75| – 3.1/2 + (5/2)2

Đáp án:

`a)`

` 25 * (-1/5)^2 -3/5`

` = 25 * (1/25) -3/5`

` = 25/25 – 3/5`

` = 1 -3/5`

` = 2/5`

`b)`

` (-2/7 : 6/14) * 8`

` = (-4/14 * 14/6) * 8`

` = -4/6 * 8`

` = -2/3 * 8`

` = -16/3`

`c)`

` |-2,75| – 3 1/2 +  (5/2)^2`

` = 2,75 – 7/2 + 25/4`

` = 11/4 + 25/4 – 7/2`

` = 36/4 – 7/2`

`  = 9 -7/2`

` = 11/2`